Heat exchanger

ABSTRACT

A flow inlet and a flow outlet are provided at one lateral end of a core. A second communication passage is provided at the other lateral end of the core to communicate between an interior of a downstream side lower tank, which is connected to a furthermost downstream side passage row that is furthermost from the flow inlet, and an interior of an upstream side lower tank, which is connected to a furthermost upstream side passage row that is furthermost from the flow outlet. The second communication passage is placed at a location that projects from a body of the core in a lateral direction or a top-to-bottom direction of the core.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by referenceJapanese Patent Application No. 2007-336862 filed on Dec. 27, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger.

2. Description of Related Art

For example, Japanese Unexamined Patent Publication No. JP2005-291659Adiscloses an evaporator as a heat exchanger. This evaporator has a core(a heat exchanging unit) that includes an upstream side row of tubes anda downstream side row of tubes, which are placed one after another in adirection of an air flow. In each row, the tubes extend in atop-to-bottom direction of the core and are stacked one after another ina lateral direction of the core. An upper tank is provided at upper endsof the tubes, and a lower tank is provided at lower ends of the tubes. Apartition plate is placed in an interior of the upper tank.

In this evaporator, refrigerant is supplied into the interior of theupper tank through a refrigerant inlet, which is provided at one lateralend of the upper tank. Then, the refrigerant flows from the interior ofthe upper tank through the downstream side row of the tubes and thelower tank and makes a U-turn. Thereafter, the refrigerant is suppliedinto the upstream side row of the tubes. Next, the refrigerant flowsthrough the upstream side row of the tubes and the lower tank and makesa U-turn. Thereafter, the refrigerant is outputted from a refrigerantoutlet, which is provided next to the refrigerant inlet at the same sideof the core. When the refrigerant flows through the tubes, therefrigerant exchanges the heat with the air, which flows outside of thetubes. Thereby, the refrigerant is evaporated.

In the above heat exchanger, the refrigerant distribution in thedirection of the air flow at the core poses the following disadvantage.That is, at a further portion of the core, which is apart from therefrigerant inlet, the refrigerant, which is discharged from the tank,tends to enter the downstream side row of the tubes. Therefore, thesupply of the refrigerant is biased to the downstream side. As a result,the desirable refrigerant performance cannot be achieved.

SUMMARY OF THE INVENTION

The present invention addresses the above disadvantage. Thus, it is anobjective of the present invention to provide a heat exchanger, whichalleviates biasing of a refrigerant flow that tends to enter adownstream side flow passage at a further portion of a core, which isapart from a refrigerant inlet.

To achieve the objective of the present invention, there is provided aheat exchanger that includes a core, a plurality of downstream sideheader tanks, a plurality of upstream side header tanks, a refrigerantinlet, a refrigerant outlet, at least one downstream side partition walland at least one upstream side partition wall. The core includes aplurality of downstream side flow passage rows and a plurality ofupstream side flow passage rows. Each of the plurality of downstreamside flow passage rows is formed with a plurality of downstream sidetubes, which extend in a top-to-bottom direction of the core and areplaced one after another in a lateral direction of the core to form aplurality of flow passages, respectively, that conduct a flow ofrefrigerant therethrough and are arranged in a row to form thedownstream side flow passage row. The downstream side flow passage rowsare placed side-by-side in the lateral direction of the core on adownstream side in a direction of an air flow, which exchanges heat withthe refrigerant. Each of the plurality of upstream side flow passagerows is formed with a plurality of upstream side tubes, which extend inthe top-to-bottom direction of the core and are placed one after anotherin the lateral direction of the core to form a plurality of flowpassages, respectively, that conduct a flow of the refrigeranttherethrough and are arranged in a row to form the upstream side flowpassage row. The upstream side flow passage rows are placed side-by-sidein the lateral direction of the core on an upstream side of thedownstream side flow passage rows in the direction of the air flow. Eachdownstream side header tank supplies the refrigerant to or receives therefrigerant from the downstream side tubes of each corresponding one ofthe downstream side flow passage rows. The plurality of downstream sideheader tanks includes at least one downstream side upper tank and atleast one downstream side lower tank. Each downstream side upper tank isconnected to upper ends of the flow passages of each corresponding oneof the downstream side flow passage rows. Each downstream side lowertank is connected to lower ends of the flow passages of eachcorresponding one of the downstream side flow passage rows. Eachupstream side header tank supplies the refrigerant to or receives therefrigerant from the upstream side tubes of each corresponding one ofthe upstream side flow passage rows. The plurality of upstream sideheader tanks includes at least one upstream side upper tank and at leastone upstream side lower tank. Each upstream side upper tank is connectedto upper ends of the flow passages of each corresponding one of theupstream side flow passage rows. Each upstream side lower tank isconnected to lower ends of the flow passages of each corresponding oneof the upstream side flow passage rows. The refrigerant inlet is locatedat one lateral side of the core and is communicated with an interior ofa corresponding one of the downstream side header tanks to supply therefrigerant to the flow passages of a corresponding one of thedownstream side flow passage rows. The refrigerant outlet is located atthe one lateral side of the core and is communicated with an interior ofa corresponding one of the upstream side header tanks to output therefrigerant from the flow passages of a corresponding one of theupstream side flow passage rows. Each downstream side partition wall isprovided in a corresponding one of the downstream side header tanks topartition an interior of the corresponding one of the downstream sideheader tanks, so that one of the downstream side flow passage rows formsan upflow passage row, in which the flow of the refrigerant becomes anupflow, on one lateral side of the downstream side partition wall, andanother one of the downstream side flow passage rows forms a downflowpassage row, in which the flow of the refrigerant becomes a downflow, onthe other lateral side of the downstream side partition wall. Eachupstream side partition wall is provided in a corresponding one of theupstream side header tanks to partition an interior of the correspondingone of the upstream side header tanks, so that one of the upstream sideflow passage rows forms an upflow passage row, in which the flow of therefrigerant becomes an upflow, on one lateral side of the upstream sidepartition wall, and another one of the upstream side flow passage rowsforms a downflow passage row, in which the flow of the refrigerantbecomes a downflow, on the other lateral side of the upstream sidepartition wall.

In one instance, a communicating means may be provided at the otherlateral side of the core opposite from the refrigerant inlet and therefrigerant outlet. The communicating means is for communicating betweenan interior of each corresponding one of the downstream side headertanks, which is connected to a furthermost one of the downstream sideflow passage rows that is furthermost from the refrigerant inlet in thelateral direction of the core, and an interior of each corresponding oneof the upstream side header tanks, which is connected to a furthermostone of the upstream side flow passage rows that is furthermost from therefrigerant outlet in the lateral direction of the core. Thecommunicating means is placed at a location that projects from a body ofthe core in one of the lateral direction and the up-to-bottom directionof the core. A portion of the refrigerant in a furthermost one of thedownstream side header tanks, which is furthermost from the refrigerantinlet in the lateral direction of the core, is conducted toward theupstream side of the air flow into a furthermost one of the upstreamside header tanks located on an upstream side thereof in the directionof the air flow after flowing through the communicating means and thenflows through the furthermost one of the upstream side flow passage rowsinto an opposed one of the upstream side header tanks, which is opposedto the furthermost one of the upstream side header tanks in thetop-to-bottom direction of the core. A rest of the refrigerant, whichremains in the furthermost one of the downstream side header tanks,flows through the furthermost one of the downstream side flow passagerows into an opposed one of the downstream side header tanks, which isopposed to the furthermost one of the downstream side header tanks inthe top-to-bottom direction of the core, and then flows toward theupstream side of the air flow into the opposed one of the upstream sideheader tanks where the rest of the refrigerant is merged with theportion of the refrigerant supplied through the communicating means.

In another instance, a lower communication passage may be provided atthe other lateral side of the core opposite from the refrigerant inletand the refrigerant outlet. The lower communication passage communicatesbetween an interior of a furthermost one of the at least one downstreamside lower tank, which is furthermost from the refrigerant inlet in thelateral direction of the core and is connected to a furthermost one ofthe downstream side flow passage rows that is furthermost from therefrigerant inlet in the lateral direction of the core, and an interiorof a furthermost one of the at least one upstream side lower tank, whichis furthermost from the refrigerant outlet in the lateral direction ofthe core and is connected to a furthermost one of the upstream side flowpassage rows that is furthermost from the refrigerant outlet in thelateral direction of the core, to conduct a portion of the refrigerantin the furthermost one of the at least one downstream side lower tankinto the furthermost one of the upstream side flow passage rows. Theportion of the refrigerant from the furthermost one of the at least onedownstream side lower tank flows into the furthermost one of the atleast one upstream side lower tank through the lower communicationpassage and then flows into the furthermost one of the at least oneupstream side upper tank after flowing upwardly thorough the furthermostone of the upstream side flow passage rows. A rest of the refrigerant,which remains in the furthermost one of the at least one downstream sidelower tank, flows upwardly through the furthermost one of the downstreamside flow passage rows into the furthermost one of the at least onedownstream side upper tank and then flows into the furthermost one ofthe at least one upstream side upper tank and is merged with the portionof the refrigerant in the furthermost one of the at least one upstreamside upper tank. The refrigerant inflow opening of the lowercommunication passage is an inlet of the lower communication passage andopens to an interior of the furthermost one of the at least onedownstream side lower tank at a location that is below lower endopenings of the downstream side tubes of the furthermost one of thedownstream side flow passage rows in the vertical direction.

In a further instance, an upper communication passage may be provided atthe other lateral side of the core opposite from the refrigerant inletand the refrigerant outlet. The upper communication passage communicatesbetween an interior of a furthermost one of the at least one downstreamside upper tank, which is furthermost from the refrigerant inlet in thelateral direction of the core and is connected to a furthermost one ofthe downstream side flow passage rows that is furthermost from therefrigerant inlet in the lateral direction of the core, and an interiorof a furthermost one of the at least one upstream side upper tank, whichis furthermost from the refrigerant outlet in the lateral direction ofthe core and is connected to a furthermost one of the upstream side flowpassage rows that is furthermost from the refrigerant outlet in thelateral direction of the core, to conduct a portion of the refrigerantin the furthermost one of the at least one downstream side upper tankinto the furthermost one of the upstream side flow passage rows. Theportion of the refrigerant from the furthermost one of the at least onedownstream side upper tank flows into the furthermost one of the atleast one upstream side upper tank through the upper communicationpassage and then flows into the furthermost one of the at least oneupstream side lower tank after flowing downwardly thorough thefurthermost one of the upstream side flow passage rows. A rest of therefrigerant, which remains in the furthermost one of the at least onedownstream side upper tank, flows downwardly through the furthermost oneof the downstream side flow passage rows into the furthermost one of theat least one downstream side lower tank and then flows into thefurthermost one of the at least one upstream side lower tank and ismerged with the portion of the refrigerant in the furthermost one of theat least one upstream side lower tank. A refrigerant inflow opening ofthe upper communication passage is an inlet of the upper communicationpassage and opens to an interior of the furthermost one of the at leastone downstream side upper tank at a location that is above upper endopenings of the downstream side tubes of the furthermost one of thedownstream side flow passage rows in the vertical direction.

In a further instance, a communicating means may be provided at theother lateral side of the core opposite from the refrigerant inlet andthe refrigerant outlet. The communicating means is for communicatingbetween an interior of each corresponding one of the downstream sideheader tanks, which is connected to a furthermost one of the downstreamside flow passage rows that is furthermost from the refrigerant inlet inthe lateral direction of the core, and an interior of each correspondingone of the upstream side header tanks, which is connected to afurthermost one of the upstream side flow passage rows that isfurthermost from the refrigerant outlet in the lateral direction of thecore. The core has an upstream side lateral plane and a downstream sidelateral plane, which are located on the upstream side and the downstreamside, respectively, in the direction of the air flow. The core is tiltedtoward the upstream side in the direction of the air flow such that theupstream side lateral plane is closer to an imaginary horizontal plane,which is placed vertically below the at least one upstream side lowertank, in comparison to the downstream side lateral plane. A portion ofthe refrigerant in a furthermost one of the downstream side headertanks, which is furthermost from the refrigerant inlet in the lateraldirection of the core, is conducted toward the upstream side of the airflow into a furthermost one of the upstream side header tanks located onan upstream side thereof in the direction of the air flow after flowingthrough the communicating means and then flows through the furthermostone of the upstream side flow passage rows into an opposed one of theupstream side header tanks, which is opposed to the furthermost one ofthe upstream side header tanks in the top-to-bottom direction of thecore. A rest of the refrigerant, which remains in the furthermost one ofthe downstream side header tanks, flows through the furthermost one ofthe downstream side flow passage rows into an opposed one of thedownstream side header tanks, which is opposed to the furthermost one ofthe downstream side header tanks in the top-to-bottom direction of thecore, and then flows toward the upstream side of the air flow into theopposed one of the upstream side header tanks where the rest of therefrigerant is merged with the portion of the refrigerant suppliedthrough the communicating means.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features andadvantages thereof, will be best understood from the followingdescription, the appended claims and the accompanying drawings in which:

FIG. 1 is a perspective view showing an evaporator (an example of a heatexchanger) according to a first embodiment of the present invention;

FIG. 2 is a partial perspective enlarged view showing a portion of acore of the evaporator;

FIG. 3 is a schematic view showing a structure and a refrigerant flow ofthe evaporator according to the first embodiment;

FIG. 4 is an exploded view showing a structure of a communicationpassage forming member of the evaporator according to the firstembodiment;

FIG. 5 is a schematic view showing a structure and a refrigerant flow ofan evaporator according to a second embodiment of the present invention;

FIG. 6 is a schematic diagram seen in a direction opposite from anX-direction, showing a positional relationship of a communicationpassage inlet and a communication passage outlet relative to adownstream side flow passage row and an upstream side flow passage rowaccording to the second embodiment;

FIG. 7 is a schematic view showing a structure and a refrigerant flow ofan evaporator according to a third embodiment of the present invention;

FIG. 8 is a schematic view showing a structure and a refrigerant flow ofan evaporator according to a fourth embodiment of the present invention;

FIG. 9 is a schematic view showing a structure and a refrigerant flow ofan evaporator according to a fifth embodiment of the present invention;

FIG. 10 is a schematic view showing a structure and a refrigerant flowof an evaporator according to a sixth embodiment of the presentinvention;

FIG. 11 is a schematic diagram seen in an X direction, showing apositional relationship of a communication passage inlet and acommunication passage outlet relative to a downstream side flow passagerow and an upstream side flow passage row according to the sixthembodiment;

FIG. 12 is a schematic view showing a structure and a refrigerant flowof an evaporator according to a seventh embodiment of the presentinvention;

FIG. 13 is a schematic view seen from a direction opposite from aZ-direction, showing a relationship of communication holes relative to adownstream side flow passage row and an upstream side flow passage rowaccording to the seventh embodiment;

FIG. 14 is a schematic view showing a structure and a refrigerant flowof an evaporator according to an eighth embodiment of the presentinvention;

FIG. 15 is a schematic view seen from a direction opposite from aZ-direction, showing a relationship of communication holes relative to adownstream side flow passage row and an upstream side flow passage rowaccording to the eighth embodiment;

FIG. 16 is a schematic view showing a structure and a refrigerant flowof an evaporator (a case where the number of refrigerant flow paths issix) according to a ninth embodiment of the present invention;

FIG. 17 is a schematic view showing a structure and a refrigerant flowof an evaporator (a case where the number of refrigerant flow paths isfive) according to a tenth embodiment of the present invention;

FIG. 18 is a schematic view showing a structure and a refrigerant flowof an evaporator (a case where the number of refrigerant flow paths isfive) according to an eleventh embodiment of the present invention;

FIG. 19 is a schematic view showing a structure and a refrigerant flowof an evaporator (a case where the number of refrigerant flow paths isfour) according to a twelfth embodiment of the present invention;

FIG. 20 is a schematic view showing a structure and a refrigerant flowof an evaporator (a case where the number of refrigerant flow paths isthree) according to a thirteenth embodiment of the present invention;

FIG. 21 is a side view showing a positioning state of an evaporatoraccording to a fourteenth embodiment of the present invention;

FIG. 22 is a partial schematic side view showing an interior of an upperheader tank at a furthermost portion of the evaporator and a refrigerantflow quantity relationship in an interior of a core of the evaporatoraccording to the fourteenth embodiment;

FIG. 23 is a partial schematic side view showing an interior of a lowerheader tank at a furthermost portion of the evaporator and a refrigerantflow quantity relationship in an interior of the core of the evaporatoraccording to the fourteenth embodiment;

FIG. 24 is a partial side view showing an upper header tank of anevaporator according to a fifteenth embodiment of the present invention;

FIG. 25 is a partial front view seen from an X-direction, showing a flowinlet at the upper header tank of FIG. 24;

FIG. 26 is a graph showing a result of a computation obtained under apredetermined condition for a relationship between a tank outer diameterand a pressure loss in an interior of the tank according to thefifteenth embodiment;

FIG. 27 is a schematic diagram for designing an appropriate condition ofa flow quantity of refrigerant, which flows in an upstream side flowpassage row, and a flow quantity of a refrigerant, which flows in adownstream side flow passage row, according to a sixteenth embodiment ofthe present invention;

FIG. 28 is a diagram showing a result of a computation of a ratiobetween a total passage cross sectional area of a branching passage anda total passage cross sectional area of a merging passage for variousnumbers of refrigerant flow paths according to the sixteenth embodiment;

FIG. 29 is a schematic view showing a structure and a refrigerant flowof an evaporator according to a seventeenth embodiment of the presentinvention;

FIG. 30 is a schematic diagram showing a modification of the evaporatorof FIG. 29;

FIG. 31 is a schematic front view showing a relationship betweencommunication passage forming member and a core of an evaporatoraccording to an eighteenth embodiment of the present invention;

FIG. 32 is a schematic partial front view showing a modification of theevaporator of FIG. 31; and

FIG. 33 is a schematic partial front view showing another modificationof the evaporator of FIG. 31.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the present invention will be described withreference to the accompanying drawings. In the following embodiments,similar components are indicated by the same reference numerals and willnot be redundantly described to simply the description. Furthermore, itshould be noted that any one or more components of one or more of thefollowing embodiments may be freely combined with any one or morecomponents of any other one or more of the following embodiments as longas there is no reason that hinders implementation of such a combination.

First Embodiment

A first embodiment of the present invention will be described withreference to FIGS. 1 to 4. FIG. 1 is a schematic perspective viewshowing an entire structure of an evaporator 1 according to the firstembodiment. FIG. 2 is a partial enlarged perspective view of a core 100,which is a heat exchanging unit of the evaporator 1. FIG. 3 is aschematic diagram showing the structure of the evaporator 1 and a flowof refrigerant therein according to the present embodiment.

The evaporator 1 of the present embodiment is a component of arefrigeration cycle, which is installed in a vehicle air conditioningsystem. The evaporator 1 serves as a heat exchanger. In thisrefrigeration cycle, the refrigerant is compressed by a compressor andbecomes the high temperature and high pressure refrigerant. Thereafter,the refrigerant is cooled through a radiator and is depressurizedthrough an expansion device to become the low temperature and lowpressure refrigerant. The refrigerant is then supplied to the evaporator1 and is evaporated therethrough. In the present embodiment, R134a (oneof hydro-fluoro-carbon refrigerants) is used as the refrigerant. Theradiator serves as a condenser, which condenses the refrigerantdischarged from the compressor.

As shown in FIG. 1, the evaporator 1 includes a core 100, an upperheader tank (forming corresponding upstream side and downstream sideupper tanks described below) 3 and a lower header tank (formingcorresponding upstream side and downstream side lower tanks describedbelow) 4. As shown in FIG. 2, the core 100 includes a plurality of tubes20, a plurality of outer fins 26 and side plates 28. The tubes 20 andthe outer fins 26 are alternately staked in one direction (hereinafter,referred to as a stacking direction). Each of the side plates 28 isplaced on an outer side of a corresponding one of opposed outermostouter fins 26 in the stacking direction. The outer fins 26 serve as heatexchanging fins. In FIGS. 1 and 2, an X-direction is the stackingdirection (lateral direction), along which the tubes 20 are placed oneafter another. Furthermore, a Z-direction is a flow direction of theair, and a Y-direction is a longitudinal direction (extending direction)of the respective tubes and corresponds to a top-to-bottom direction ofthe core 100. In FIG. 1, a width W of the core 100 is measured in theX-direction, and a height H of the core 100 is measured in theY-direction. Also, a thickness T of the core 100 is measured in theZ-direction.

In the core 100 of the evaporator 1, the vertically extending tubes 20are arranged in a plurality of rows, each of which extends in theX-direction. The rows of the tubes 20 include at least two rows (anupstream side row and a downstream side row) of tubes 20, which areplaced one after another in the Z-direction, i.e., the direction of theair flow (hereinafter, also simply referred to as the air flowdirection). The air serves as an external fluid, which exchanges theheat with the refrigerant that flows through the tubes 20. Each tube 20is formed, for example, by bending a thin aluminum strip plate into agenerally flat tubular member that has a generally planar cross section,which is generally planar in a direction perpendicular to thelongitudinal direction (internal fluid passage direction) of the tubularmember. Inner fins (not shown) are provided in the interior of the tube20 and are joined to an inner surface of the tube 20.

In the core 100, the rows of the tubes 20 are divided into apredetermined number of downstream side flow passage rows 21 of thetubes 20 (these tubes 20 will be hereinafter referred to as tubes 20 a)placed on the downstream side in the air flow direction and apredetermined number of upstream side flow passage rows 22 of the tubes20 (these tubes will be hereinafter referred to as tubes 20 b) placed onthe upstream side in the air flow direction with respect to thedownstream side flow passage rows 21 of the tubes 20 a. In eachdownstream side flow passage row 21, the tubes 20 a are placed one afteranother in the X-direction (lateral direction) to form a plurality offlow passages. Also, in each upstream side flow passage row 22, thetubes 20 b are placed one after another in the X-direction (lateraldirection) to form a plurality of flow passages. The downstream sideflow passage rows 21 and the upstream side flow passage rows 22 arerespectively placed on the downstream side and the upstream side in theair flow direction and are integrated together to form the core 100.Here, the number of the downstream side flow passage rows 21 and thenumber of the upstream side flow passage rows 22 are determined based ona pattern of the refrigerant flow (hereinafter, referred to as arefrigerant flow pattern) in the core 100. Furthermore, with referenceto FIG. 2, a thickness Ta of the downstream side flow passage row 21,which is measured in the direction of the air flow, is set to begenerally the same as a thickness Th of the upstream side flow passagerow 22, which is measured in the direction of the air flow, in thisembodiment.

In each downstream side flow passage row 21, the refrigerant in each ofthe tubes 20 a flows in a common direction. Furthermore, the downstreamside flow passage rows 21 are communicated with each other throughdownstream side header tanks 11 (the downstream side upper tank of theupper header tank 3 and the downstream side lower tank of the lowerheader tank 4). In each upstream side flow passage row 22, therefrigerant in each of the tubes 20 b flows in a common direction.Furthermore, the upstream side flow passage rows 22 are communicatedwith each other through upstream side header tanks 12 (the upstream sideupper tank of the upper header tank 3 and the upstream side lower tankof the lower header tank 4).

The outer fins 26 are corrugate fins and have, for example, louvers (notshown) formed on the surfaces of the outer fins 26 to increase the heatexchange efficiency. The outer fins 26 are joined to the outer surfacesof the tube 20 (tubes 20 a, 20 b) by brazing.

The side plates 28 serve as reinforcing members, which reinforce thestructural strength of the core 100. Each side plate 28 is formedthrough a press working process of an aluminum plate. Each of twoopposed longitudinal end portions of each side plate 28 is configuredinto a flat plate form, and the rest of the side plate, which is otherthan the longitudinal end portions, is configured into a generallyU-shaped form, which opens toward the outer side in the stackingdirection of the tubes 20 (20 a, 20 b). Furthermore, the side plate 28is fixed to the corresponding outer fin 26 by brazing.

The downstream side header tanks 11 include the downstream side uppertank (downstream side upper tank portion) 31 and the downstream sidelower tank (downstream side lower tank portion) 41. The downstream sideupper tank 31 is connected to upper ends of the tubes 20 a of thedownstream side flow passage rows 21, and the downstream side lower tank41 is connected to lower ends of the tubes 20 a of the downstream sideflow passage rows 21. These upper and lower tanks 31, 41 form chambers(interior spaces), to which the refrigerant from the tubes 20 a of thedownstream side flow passage rows 21 is supplied and from which therefrigerant is distributed into the tubes 20 a of the downstream sideflow passage rows 21.

A connector 5 in a form of a block is fixed to a left side end (an endin a direction opposite from the X-direction) of the downstream sideupper tank 31 by brazing. The connector 5 has a flow inlet 51, whichserves as a refrigerant inlet that is communicated with the interior ofthe downstream side header tank 11 to conduct the refrigerant into thecore 100. The flow inlet 51 is communicated with a left end of thedownstream side lower tank 41 (an end in the direction opposite from theX-direction) through a side flow passage 2 defined in, for example, theinterior side of the side plate 28.

The upstream side header tanks 12 include the upstream side upper tank32 and the upstream side lower tank 42. The upstream side upper tank 32is connected to upper ends of the tubes 20 b of the upstream side flowpassage rows 22, and the upstream side lower tank 42 is connected tolower ends of the tubes 20 b of the upstream side flow passage rows 22.These upper and lower tanks 32, 42 form chambers (interior spaces), towhich the refrigerant from the tubes 20 a of the upstream side flowpassage rows 22 is supplied and from which the refrigerant isdistributed into the tubes 20 a of the upstream side flow passage rows22.

The connector 5 in the form of the block is fixed to a left side end (anend in a direction opposite from the X-direction) of the upstream sideupper tank 32 by brazing. The connector 5 has a flow outlet 52, whichserves as a refrigerant outlet that is communicated with the interior ofthe upstream side header tank 12 to conduct the refrigerant out of thecore 100 toward the external device in the refrigerant cycle. Asdiscussed above, the flow inlet 51 and the flow outlet 52 arerespectively provided to the end of the downstream side header tank 11and the end of the upstream side header tank 12 on the common lateralside of the core 100.

The upper header tank 3 is divided into two halves, which are referredto as a tank header and a plate header, in the longitudinal direction(the extending direction, the internal fluid passage direction) of thetubes 20 (20 a, 20 b). The tank header is placed on the side oppositefrom the tubes 20 (20 a, 20 b), and the plate header is placed on theside where the tubes 20 (20 a, 20 b) are located. Each correspondinglongitudinal end opening of the upper header tank 3 is closed with acap. The upper header tank 3 includes the downstream side upper tank(downstream side upper tank portion) 31 and the upstream side upper tank(upstream side upper tank portion) 32. Each of the tank header and theplate header has a cross section that includes two semi-spherical partsor two semi-rectangular parts, which are connected side-by-side.Furthermore, each of the tank header and the plate header is formedthrough a press working process of an aluminum plate. The tank headerand the plate header are engaged with each other and are securely brazedtogether to form a tubular body, in which the two interior spaces areplaced one after another in the air flow direction to form thedownstream side upper tank 31 and the upstream side upper tank 32. Thecap, which is formed through a press working of an aluminum plate, isbrazed to each corresponding longitudinal end opening of the downstreamside upper tank 31 and of the upstream side upper tank 32 to close thesame.

A plurality of separators (see FIG. 3) is fixed by brazing in the upperheader tank 3 to divide each of the two internal spaces into two partsin the X-direction (the lateral direction). Specifically, the interiorof the upstream side upper tank 32 is divided by the separator (upstreamside upper partition wall) 32 a into two spaces in the lateral directionof the core 100. Also, the interior of the downstream side upper tank 31is divided by the separator (downstream side upper partition wall) 31 ainto two spaces in the lateral direction of the core 100.

The downstream side flow passage rows 21 include downstream side flowpassage rows 21 a, 210 (serving as upflow passage rows) and a downstreamside flow passage row 21 b (serving as a downflow passage row). Theseparator 31 a is provided in the downstream side upper tank 31 in sucha manner that one of the downstream side flow passage rows 21 a, 210 isplaced adjacent to the separator 31 a on one lateral side thereof, andthe downstream side flow passage row 21 b is placed adjacent to theseparator 31 a on the other lateral side thereof, thereby dividingbetween the upflow and the downflow. The, upstream side flow passagerows 22 include upstream side flow passage rows 22 a, 220 (serving asupflow passage rows) and an upstream side flow passage row 22 b (servingas a downflow passage row). The separator 32 a is provided in theupstream side upper tank 32 in such a manner that one of the upstreamside flow passage rows 22 a, 220 is placed adjacent to the separator 32a on one lateral side thereof, and the upstream side flow passage row 22b is placed adjacent to the separator 32 a on the other lateral sidethereof, thereby dividing between the upflow and the downflow.

In the right side region of the downstream side upper tank 31, which islocated on the right side of the separator 31 a (the side of theseparator 31 a in the X-direction) in FIG. 3, a plurality ofcommunication holes 300 is provided to communicate between the rightlateral side space of the downstream side upper tank 31 and the rightlateral side space of the upstream side upper tank 32.

The communication holes 300 are formed through a partition wall, whichpartitions the tank interior at the other lateral side, which isopposite from the lateral side wherein the flow inlet 51 and the flowoutlet 52 are provided. The communication holes 300 serve as acommunicating means for communicating between the interior of thefurthermost downstream side upper tank 311 (also referred to as afurthermost downstream side upper tank portion, a furthermost downstreamside upper tank interior, or a furthermost downstream side upper tankchamber of the downstream side upper tank 31), which is connected to thedownstream side flow passage row 210 that is furthermost from the flowinlet 51 (hereinafter, also referred to as a furthermost downstream sideflow passage row 210 at the furthermost portion of the core 100, whichis furthermost from the flow inlet 51 and the flow outlet 52 in theX-direction), and the interior of the furthermost upstream side uppertank 321 (also referred to as a furthermost upstream side upper tankportion, a furthermost upstream side upper tank interior, or afurthermost upstream side upper tank chamber of the upstream side uppertank 32), which is connected to the upstream side flow passage row 220that is furthermost from the flow outlet 52 (hereinafter, also referredto as a furthermost upstream side flow passage row 220 at thefurthermost portion of the core 100). The communication holes 300 alsoform a part of a first communication passage 33, through which therefrigerant in the furthermost downstream side upper tank 311 flowstoward the upstream side of the air flow and finally into thefurthermost upstream side upper tank 321.

The first communication passage 33 is an upper communication passage,which communicates between the interior of the furthermost downstreamside upper tank 311, which is furthermost from the flow inlet 51 in thelateral direction, and the furthermost upstream side upper tank 321,which is furthermost from the flow outlet 52 in the lateral direction.The interior of the downstream side upper tank 311 is the furthermostone of the two partitioned spaces, which are partitioned from each otherin the lateral direction by the separator 31 a, with respect to the flowinlet 51. The interior of the upstream side upper tank 321 is thefurthermost one of the two partitioned spaces, which are partitionedfrom each other in the lateral direction by the separator 32 a, withrespect to the flow outlet 52.

The lower header tank 4 is similar to the upper header tank 3 andthereby includes the tank header and the plate header to form thetubular body. Caps are provided to longitudinal end portions,respectively, of the tubular body. The lower header tank 4 includes thedownstream side lower tank 41 and the upstream side lower tank 42.

A plurality of separators (see FIG. 3) is fixed by brazing in the lowerheader tank 3 to divide each of the two internal spaces into two partsin the X-direction (the lateral direction). Specifically, the interiorof the upstream side lower tank 42 is divided by the separator(downstream side lower partition wall) 42 a into two spaces in thelateral direction of the core 100. Also, the interior of the downstreamside lower tank 41 is divided by the separator (downstream side lowerpartition wall) 41 a into two spaces in the lateral direction of thecore 100.

The separator 41 a is provided in the downstream side lower tank 41 insuch a manner that one of the downstream side flow passage rows 21 a,210 is placed adjacent to the separator 41 a on one lateral sidethereof, and the downstream side flow passage row 21 b is placedadjacent to the separator 41 a on the other lateral side thereof,thereby dividing between the upflow and the downflow. The separator 42 ais provided in the upstream side lower tank 42 in such a manner that oneof the upstream side flow passage rows 22 a, 220 is placed adjacent tothe separator 42 a on one lateral side thereof, and the upstream sideflow passage row 22 b is placed adjacent to the separator 42 a on theother lateral side thereof, thereby dividing between the upflow and thedownflow.

In the right side region of the downstream side lower tank 41, which islocated on the right side of the separator 41 a (the side of theseparator 41 a in the X-direction) in FIG. 3, a second communicationpassage 43 is provided to communicate between the right lateral sidespace of the downstream side lower tank 41 and the right lateral sidespace of the upstream side lower tank 42.

The second communication passage 43 is a lower communication passage (acommunicating means), which communicates between the interior of thefurthermost downstream side lower tank 411 (a furthermost downstreamside lower tank portion, a furthermost downstream side lower tankinterior, or a furthermost downstream side lower tank chamber of thedownstream side lower tank 41), which is furthermost from the flow inlet51 in the lateral direction, and the furthermost upstream side lowertank 421 (a furthermost upstream side lower tank portion, a furthermostupstream side lower tank interior, or a furthermost upstream side lowertank chamber of the upstream side lower tank 42), which is furthermostfrom the flow outlet 52 in the lateral direction. The interior of thedownstream side lower tank 411 is the furthermost one of the twopartitioned spaces, which are partitioned from each other in the lateraldirection by the separator 41 a, with respect to the flow inlet 51. Theinterior of the upstream side lower tank 421 is the furthermost one ofthe two partitioned spaces, which are partitioned from each other in thelateral direction by the separator 42 a, with respect to the flow outlet52.

The second communication passage 43 is formed in an interior of acommunication passage forming member 44. A communication passage inlet441 a of the second communication passage 43, through which therefrigerant is supplied into the second communication passage 43,includes one or more holes that extend through in the X-direction (thelateral direction) to communicate between the interior of thefurthermost downstream side lower tank 411 and the interior of thecommunication passage forming member 44. A communication passage outlet441 b of the second communication passage 43, through which therefrigerant is outputted from the second communication passage 43,includes one or more holes that extend through in the X-direction (thelateral direction) to communicate between the interior of thecommunication passage forming member 44 and the interior of thefurthermost downstream side lower tank 421.

The communication passage forming member 44 is a separate component,which is formed separately from the downstream side lower tank 411 andthe upstream side lower tank 421 and is integrally fixed to thedownstream side lower tank 411 and the upstream side lower tank 421 by,for example, brazing. The communication passage forming member 44 isplaced at a location, which projects laterally from the body of the core100 (the body of the core 100 being made by the refrigerant conductingtubes 20 and the fins 26). In the present embodiment, the communicationpassage forming member 44 is configured into a box shape that projectslaterally from the furthermost downstream side lower tank 411.Furthermore, the communication passage forming member 44 is made of thematerial that is similar to or is the same as that of the furthermostdownstream side lower tank 411.

FIG. 4 is an exploded view showing the communication passage formingmember 44. As shown in FIG. 4, the communication passage forming member44 includes a planar member 441 and a dome member 44 b. The planarmember 441 has the communication passage inlet 441 a and thecommunication passage outlet 441 b and is joined to the downstream sidelower tank 411 and the upstream side lower tank 421. The dome member 44b is joined to the planar member 441 and has a projecting portion 44 a,which projects in the X-direction (lateral direction) away from theplanar member 441 to define a predetermined space therein and thereby todefine the second communication passage 43.

The communication passage forming member 44 may be assembled as follows.First, the planar member 441 is joined to the downstream side lower tank411 and the upstream side lower tank 421 by, for example, brazing, suchthat the communication passage inlet 441 a and the communication passageoutlet 441 b are respectively aligned with a lateral side end opening411 a of the downstream side lower tank 411 and a lateral side endopening 421 a of the upstream side lower tank 421. Then, the dome member44 b is joined to the planar member 441 by, for example, brazing, suchthat the communication passage inlet 441 a and the communication passageoutlet 441 b are opposed to a recess, which is formed inside of theprojecting portion 44 a.

With the above construction, a portion of the refrigerant in thefurthermost downstream side lower tank 411 is supplied into the secondcommunication passage 43 through the communication passage inlet 441 aand flows toward the upstream side of the air flow to enter thefurthermost upstream side lower tank 421 through the communicationpassage outlet 441 b. Then, this refrigerant in the furthermost upstreamside lower tank 421 flows upwardly through the furthermost upstream sideflow passage row 220 and then flows into the furthermost upstream sideupper tank 321, which is opposite from the furthermost upstream sidelower tank 421 in the top-to-bottom direction of the core 100. Theremaining refrigerant (the rest of the refrigerant) in the furthermostdownstream side lower tank 411 flows upwardly through the furthermostdownstream side flow passage row 210 and is supplied into thefurthermost downstream side upper tank 311, which is opposite from thefurthermost downstream side lower tank 411 in the top-to-bottomdirection of the core 100. Then, this refrigerant flows toward theupstream side of the air flow and enters into the upstream side uppertank 321 where this refrigerant is merged with the branched portion ofthe refrigerant, which has passed through the second communicationpassage 43.

Tube insertion inlets and side plate insertion inlets are provided atgenerally equal pitches in the longitudinal direction in a wall surfaceof each of the upper and lower header tanks 3, 4. The longitudinal endportions of each tube 20 and the longitudinal end portions of each sideplate 28 are received into and are joined to the corresponding tubeinsertion inlets and the corresponding side plate insertion inlets by,for example, brazing. In this way, the tubes 20 are communicated withthe interior space of each of the upper and lower header tanks 3, 4, andthe longitudinal end portions of each side plate 28 are supported by theupper and lower header tanks 3, 4.

The refrigerant flow pattern in the evaporator 1 of the presentembodiment is constructed from three downstream side flow passage rowsand three upstream side flow passage rows. The three downstream sideflow passage rows include one downstream side flow passage row 21 b (therefrigerant upflow portion), one downstream side flow passage row 21 b(the refrigerant downflow portion) and one furthermost downstream sideflow passage row 210. The three upstream side flow passage rows includeone furthermost upstream side flow passage row 220, one upstream sideflow passage row 22 b (the refrigerant downflow portion) and oneupstream side flow passage row 22 a (the refrigerant upflow portion).

In this instance, the number of the refrigerant flow paths is counted inthe following manner. Specifically, the refrigerant flow in thefurthermost downstream side flow passage row 210 and refrigerant flow inthe furthermost upstream side flow passage row 220 are collectivelycounted as one refrigerant flow path. Furthermore, the number (two inthis instance) of the other downstream side flow passage rows 21 a, 21b, which are other than the furthermost downstream side flow passage row210, and the number (two in this instance) of the other upstream sideflow passage rows 22 a, 22 b, which are other than the furthermostupstream side flow passage row 220, are also counted. Therefore, thenumber of the refrigerant flow paths in the core 100 is five in thepresent embodiment. Furthermore, the refrigerant flow pattern in theevaporator 1 is expressed by the number of path(s) in the downstreamside flow passage rows 21, the number of path(s) in the upstream sideflow passage row 22 and the number of path(s) of the full-path portion200 (the portion where the branched flow of the refrigerant, which isbranched from the downstream side to the upstream side, flows upwardlyin the top-to-bottom direction of the core 100). These numbers arewritten one after another according to the flow order of the refrigerantin the evaporator 1 and are thereby expressed as a 2-1-2 refrigerantflow pattern in this instance.

Next, the flow of the refrigerant in the evaporator 1 will besequentially described. The refrigerant from the external constituentcomponent of the refrigeration cycle is supplied into the downstreamside lower tank 41, which is the space on the left lateral side of theseparator 41 a (the side of the separator 41 a, which is opposite fromthe X-direction) through the upper flow inlet 51 and the side flowpassage 2. Then, the refrigerant flows upwardly through the downstreamside flow passage row 21 a (the first path). Next, the flow direction ofthis refrigerant is reversed in the interior of the downstream sideupper tank 31, which is the space on the left lateral side of theseparator 31 a (the side of the separator 31 a, which is opposite fromthe X-direction), and thereafter the refrigerant flows downwardlythrough the downstream side flow passage row 21 b (the second path).Thereafter, this refrigerant is supplied into the interior of thefurthermost downstream side lower tank 411.

Then, a portion of the refrigerant in the downstream side lower tank 411is branched into the second communication passage 43. Then, in thesecond communication passage 43, the branched portion of the refrigerantflows in the X-direction and then flows toward the upstream side of theair flow (the side opposite from the Z-direction), and thereafter thebranched portion of the refrigerant flows in the direction opposite fromthe X-direction and is supplied into the upstream side lower tank 421.Thereafter, this branched portion of the refrigerant flows upwardlythrough the furthermost upstream side flow passage row 220 (the thirdpath, the full-path portion 200) into the upstream side upper tank 321.

In contrast, the remaining refrigerant (the rest of the refrigerant) inthe downstream side lower tank 411, which is other than the branchedportion of the refrigerant, flows upwardly through the furthermostdownstream side flow passage row 210 (the third path, the full-pathportion 200) and then flows from the interior of the downstream sideupper tank 311 toward the upstream side of the air flow into theupstream side upper tank 321 through the communication holes 300 in thefirst communication passage 33. Then, this refrigerant is merged withthe above branched portion of the refrigerant, which is supplied throughthe furthermost upstream side flow passage row 220 after flowingupwardly therethrough. That is, the refrigerant in the furthermostdownstream side flow passage row 210 and the refrigerant in thefurthermost upstream side flow passage row 220 flow upwardly parallel toone another.

The flow direction of the merged refrigerant, which is merged in theinterior of the upstream side upper tank 321, is reversed, and thisrefrigerant flows downwardly through the upstream side flow passage row22 b (the fourth path). Then, the flow direction of this refrigerant isreversed once again in the upstream side lower tank 42, and thereby therefrigerant flows upwardly through the upstream side flow passage row 22a (the fifth path). Thereafter, this refrigerant flows to the outside ofthe core 100 from the upstream side upper tank 32 through the flowoutlet 52.

Normally, the evaporator has the function of cooling the air by takingthe heat of vaporization from the air at the time of vaporization of theliquid phase refrigerant (hereinafter, referred to as the liquidrefrigerant). Therefore, in the evaporator, the refrigerant is in thetwo-phase (gas phase and liquid phase) state. In the operating state ofthe evaporator, a gas-liquid density ratio is about 80 to 95 times(i.e., liquid phase density:gas phase density=80-95:1) in the case ofthe R134a refrigerant and is about 8 to 9 times in the case of thecarbon dioxide refrigerant. Therefore, the gas/liquid separationsubstantially occurs. Furthermore, an enlarged flow passage crosssectional area is provided at the tank as a refrigerant pressure lossreducing means. However, when this measure is taken, the refrigerantflow velocity at the tank is reduced, so that the gas/liquid separationis further promoted, thereby causing a reduced performance. Furthermore,there is a strong market demand for an evaporator having a simplestructure, in which the refrigerant flow passage is simplified.

The evaporator of the present embodiment addresses the above demand andhas the following structure. The evaporator has the flow inlet 51 andthe flow outlet 52, which are provided at the one lateral end portion ofthe evaporator on the same lateral side. The second communicationpassage 43 (the lower communication passage) is provided to the oppositelateral side of the core 100, which is opposite from the side where theflow inlet 51 and the flow outlet 52 are located, to communicate betweenthe interior of the downstream side lower tank 411, which is connectedto the furthermost downstream side flow passage row 210 that isfurthermost from the flow inlet 51, and the interior of the upstreamside lower tank 421, which is connected to the furthermost upstream sideflow passage row 220 that is furthermost from the flow outlet 52. Thesecond communication passage 43 conducts the portion of the refrigerantin the furthermost downstream side lower tank 411, which is furthermostfrom the flow inlet 51, into the upstream side lower tank 421 to supplythe refrigerant into the furthermost upstream side flow passage row 220.The second communication passage 43 is placed at the location thatprojects laterally or vertically (or in the top-to-bottom direction)from the body of the core 100.

The refrigerant, which has passed through the multiple downstream sideflow passage rows 21 upwardly and downwardly multiple turns in theS-shaped path, gets the inertial force and reaches the furthermostdownstream side lower tank 411. With the above structure, therefrigerant flows through the second communication passage 43 (the lowercommunication passage), which is placed at the location that projectslaterally from the body of the core 100. Thus, the refrigerant can getthe additional inertial force, and thereby the refrigerant in thedownstream side lower tank 411 can be supplied in the greater amount tothe furthermost upstream side flow passage row 220. The above effect ismore prominent in the evaporator that has the thickness (the thicknessin the air flow direction) T of the core 100, which is equal to or lessthan 70 mm.

The heat exchanger, which has the above structure, can reduce oralleviate the transitional period temperature distribution (transitionalperiod temperature difference) between an on-time and an off-time of thecompressor. When this heat exchanger is applied as the evaporator of thevehicle air conditioning system, the comfortableness of the occupant ofthe vehicle can be improved. Furthermore, the anti-frost performance ofthe evaporator can be improved to improve the cooling performance of theair conditioning system.

Furthermore, in the case where the refrigerant flow quantity isrelatively small at the time of, for example, a low load operation, evenin the upstream side flow passage, the flow of the refrigerant, whichhas passed through the second communication passage 43, is biased towardthe downstream side of the air flow. Therefore, when the entirefurthermost part of the core 100 is viewed, the condition of therefrigerant inflow in the core width direction is reversed between thedownstream side part of the furthermost portion of the core 100 and theupstream side part of the furthermost portion of the core 100, so thatthey can be compensated with each other to implement the self adjustingfunction.

Furthermore, in the case of the evaporator 1 where the flow inlet 51 andthe flow outlet 52 are provided together at the one lateral side of thecore 100 in the lateral direction of the core 100, the adjacent area ofthe upstream side flow passage row 22, which is adjacent to the flowoutlet 52, serves as a refrigerant superheating area. Therefore, theportion of the core 100, in which the refrigerant tends to be stagnated,is the furthermost downstream side flow passage row, which is placedfurthermost from the flow inlet 51 and the flow outlet 52 and contactswith the cooler air. In the evaporator 1 of the present embodiment, theoccurrence of the stagnation of the liquid refrigerant can be reduced oralleviated.

Furthermore, the evaporator 1 has the second communication passage 43(the lower communication passage), which communicates between theinterior of the furthermost downstream side lower tank 411 and theinterior of the furthermost upstream side lower tank 421, and the firstcommunication passage 33 (the upper communication passage), whichcommunicates between the interior of the furthermost downstream sideupper tank 311 and the interior of the furthermost upstream side uppertank 321. In this structure, the remaining refrigerant in thefurthermost downstream side lower tank 411 flows upwardly through thefurthermost downstream side flow passage row 210 and then flows towardthe upstream side of the air flow through the first communicationpassage 33 and finally into the upstream side upper tank 321 where theremaining refrigerant is merged with the branched refrigerant, which hasflown upwardly through the furthermost upstream side flow passage row220 upon passing through the second communication passage 43 (the lowercommunication passage).

With the above structure, it is possible to limit the flow tendency ofthe refrigerant in the furthermost downstream side lower tank 411 intothe downstream side flow passage row 210. Thereby, it is possible tosupply the greater amount of the refrigerant into the upstream side flowpassage row 220.

The refrigerant pressure loss of the evaporator 1 gets bigger toward theevaporator outlet side. Therefore, it is desirable to have therefrigerant, which has completed the heat exchange, at the locationadjacent to the flow outlet 52. Since the flow outlet 52 is provided tothe end portion of the upstream side upper tank 32, it is desirable thatthe upstream side flow passage row 22 a, which conducts the finalrefrigerant flow in the upstream side flow passage rows 22, is therefrigerant upflow portion. Furthermore, since the furthermost upstreamside flow passage row 220 (the third path), which is furthermost fromthe flow outlet 52, is also the refrigerant upflow portion, it isdesirable that the upstream side flow passage row 22 b (the fourth path)is the refrigerant downflow portion.

Second Embodiment

The evaporator 1 according to a second embodiment of the presentinvention is a modification of the first embodiment and will bedescribed with reference to FIGS. 5 and 6. FIG. 5 is a schematic diagramshowing the structure of the evaporator 1 and the flow of refrigeranttherein according to the present embodiment. FIG. 6 is a schematicdiagram showing a positional relationship of the communication passageinlet 441 a and the communication passage outlet 441 b relative to thedownstream side flow passage row 210 and the upstream side flow passagerow 220.

In the present embodiment, the first communication passage 33 (the uppercommunication passage) of the evaporator 1 of FIG. 3 is modified and isthereby placed at a location, which projects laterally from the body ofthe core 100 in the X-direction (the lateral direction) in a mannersimilar to the second communication passage 43. Other than this point,the evaporator of the present embodiment is the same as the evaporator 1of FIG. 3 and provides the same effects and the same advantages as thoseof the evaporator 1 of FIG. 3.

The first communication passage 33 is formed in an interior of acommunication passage forming member 34. A communication passage inlet341 a of the first communication passage 33, through which therefrigerant is supplied into the first communication passage 33,includes one or more holes that extend through in the X-direction (thelateral direction) to communicate between the interior of thefurthermost downstream side upper tank 311 and the interior of thecommunication passage forming member 34. A communication passage outlet341 b of the first communication passage 33, through which therefrigerant is outputted from the first communication passage 33,includes one or more holes that extend through in the X-direction (thelateral direction) to communicate between the interior of thecommunication passage forming member 34 and the interior of thefurthermost upstream side upper tank 321.

The communication passage forming member 34 is a separate component,which is formed separately from the downstream side upper tank 311 andthe upstream side upper tank 321 and is integrally fixed to thedownstream side upper tank 311 and the upstream side upper tank 321 by,for example, brazing. The communication passage forming member 34 isplaced at the location, which projects laterally from the body of thecore 100. In the present embodiment, the communication passage formingmember 34 is configured into a box shape that projects laterally fromthe furthermost downstream side upper tank 311. Furthermore, thecommunication passage forming member 34 is made of the material that issimilar to or the same as that of the furthermost downstream side uppertank 311.

As shown in FIG. 6, the communication passage inlet 441 a (a refrigerantinflow opening) is opened to the interior of the furthermost downstreamside lower tank 411 and is located on a lower side of lower end openings210 a of the tubes 20 a of the furthermost downstream side flow passagerow 210 in the vertical direction (gravitational direction).

For the comparative purpose, it is now assumed that the refrigerant inthe furthermost flow passage rows 210, 220 form the upflow, and therefrigerant inflow opening of the second communication passage opens inthe furthermost downstream side lower tank only on an upper side of thelower end openings of the tubes of the furthermost flow passage rows210, 220 in the vertical direction. In such a case, the lower endopenings of the tubes of the furthermost flow passage row are closer tothe liquid surface of the refrigerant in the tank in comparison to therefrigerant inflow opening of the second communication passage, so thatthe refrigerant tends to flow into the furthermost downstream side flowpassage row 210, and thereby the refrigerant cannot easily flow into thefirst communication passage through the refrigerant inflow opening. Withthe above structure of the present embodiment, it is possible to limitthe flow tendency of the refrigerant in the furthermost downstream sidelower tank into the downstream side flow passage row, and thereby it ispossible to supply the greater amount of the refrigerant into theupstream side flow passage row. As a result, the heat exchangeperformance of the evaporator can be improved.

Furthermore, it is desirable that an upper end of the opening of thecommunication passage inlet 441 a (the refrigerant inflow opening) islocated on the lower side of the lower end openings 210 a of the tubes20 a of the furthermost downstream side flow passage row 210.

Third Embodiment

The evaporator 1 according to a third embodiment of the presentinvention is a modification of the evaporator 1 of the first embodimentand will be described with reference to FIG. 7. FIG. 7 is a schematicdiagram showing the structure of the evaporator 1 and the flow ofrefrigerant therein according to the present embodiment.

The present embodiment differs from that of FIG. 3 such that the secondcommunication passage 43 (the lower communication passage) of theevaporator 1 of FIG. 3 is modified and is thereby placed at a location,which projects downwardly from the body of the core 100 in the verticaldirection (the direction opposite from the Y-direction). Other than thispoint, the evaporator of the present embodiment is the same as theevaporator 1 of FIG. 3 and provides the same effects and the sameadvantages as those of the evaporator 1 of FIG. 3.

In the case of the present embodiment, the communication passage formingmember 44A, which forms the second communication passage 43, is providedintegrally with the lower surfaces of the furthermost downstream sidelower tank 411 and the furthermost upstream side lower tank 421, whichare located at the lateral end portion of the core 100 in theX-direction. The communication passage forming member 44A is placedinward of two lateral ends of the core 100 in the lateral direction ofthe core 100. In this way, a dead space is reduced to effectively usethe installation space for placing the heat exchanger, and the size ofthe core 100 in the width direction can be increased. Thus, it ispossible to implement the design that improves the effective heatexchange surface area of the core 100.

The communication passage inlet 441 a of the second communicationpassage 43, through which the refrigerant is supplied into the secondcommunication passage 43, includes one or more holes that extend througha lower surface of the furthermost downstream side lower tank 411 and anupper surface of the communication passage forming member 44A in theY-direction (the vertical direction) to communicate between the interiorof the furthermost downstream side lower tank 411 and the interior ofthe communication passage forming member 44A. The communication passageoutlet 441 b of the second communication passage 43, through which therefrigerant is outputted from the second communication passage 43,includes one or more holes that extend through a lower surface of thefurthermost upstream side lower tank 421 and an upper surface of thecommunication passage forming member 44A in the Y-direction (thevertical direction) to communicate between the interior of thecommunication passage forming member 44A and the interior of thefurthermost downstream side lower tank 421.

The communication passage forming member 44A is a separate component,which is formed separately from the downstream side lower tank 411 andthe upstream side lower tank 421 and is integrally fixed to thedownstream side lower tank 411 and the upstream side lower tank 421 by,for example, brazing.

In the evaporator of the present embodiment, the second communicationpassage 43 is placed at the location, which projects downwardly from thebody of the core 100 in the vertical direction (or in the top-to-bottomdirection of the core 100). The refrigerant, which has passed throughthe multiple downstream side flow passage rows 21 upwardly anddownwardly multiple turns in the S-shaped path, gets the inertial forceand reaches the furthermost downstream side lower tank 411. Thisrefrigerant flows through the second communication passage 43 (the lowercommunication passage), which is placed at the location that projectsdownwardly from the body of the core 100 in the vertical direction.Thus, the refrigerant can get the additional inertial force by thegravity to promote the vertically downward flow of the refrigerant, andthereby the refrigerant in the downstream side lower tank 411 can besupplied in the greater amount to the furthermost upstream side flowpassage row 220.

Fourth Embodiment

The evaporator 1 according to a fourth embodiment of the presentinvention is a modification of the evaporator 1 of the first embodimentand will be described with reference to FIG. 8. FIG. 8 is a schematicdiagram showing the structure of the evaporator and the flow ofrefrigerant therein according to the present embodiment.

The evaporator of the present embodiment differs from the evaporator 1of FIG. 3 with respect to the following points. That is, the refrigerantflow pattern is different from that of FIG. 3, and the flow of therefrigerant in the furthermost flow passage row is the downflow.Furthermore, the first communication passage 33A is placed at alocation, which projects laterally from the body of the core 101. InFIG. 8, components similar to those of FIG. 3 will be indicated by thesame reference numerals. Other than this point, the evaporator of thepresent embodiment is the same as the evaporator 1 of FIG. 3 andprovides the same effects and the same advantages as those of theevaporator 1 of FIG. 3.

The refrigerant flow pattern in the evaporator 1 of the presentembodiment is constructed from two downstream side flow passage rows andtwo upstream side flow passage rows. The two downstream side flowpassage rows include one downstream side flow passage row 21 a (therefrigerant upflow portion) and one furthermost downstream side flowpassage row 211 (the refrigerant downflow portion). The two upstreamside flow passage rows include one furthermost upstream side flowpassage row 221 (the refrigerant downflow portion) and one upstream sideflow passage row 22 a (the refrigerant upflow portion).

In this instance, the number of the refrigerant flow paths is three.Furthermore, the refrigerant flow pattern in the evaporator 1 isexpressed by the number of path(s) in the downstream side flow passagerows 21, the number of path(s) in the upstream side flow passage row 22and the number of path(s) of the full-path portion 201 (the portionwhere the branched flow of the refrigerant from the downstream side tothe upstream side flows downwardly). These numbers are written one afteranother according to the flow order of the refrigerant in the evaporator1 and are thereby expressed as a 1-1-1 refrigerant flow pattern in thisinstance.

The first communication passage 33A is formed in the interior of thecommunication passage forming member 34A. A communication passage inlet341 a of the first communication passage 33A, through which therefrigerant is supplied into the first communication passage 33A,includes one or more holes that extend through in the X-direction (thelateral direction) to communicate between the interior of thefurthermost downstream side upper tank 311 and the interior of thecommunication passage forming member 34A. A communication passage outlet341 b of the first communication passage 33A, through which therefrigerant is outputted from the first communication passage 33A,includes one or more holes that extend through in the X-direction (thelateral direction) to communicate between the interior of thecommunication passage forming member 34A and the interior of thefurthermost upstream side upper tank 321.

The communication passage forming member 34A is a separate component,which is formed separately from the downstream side upper tank 311 andthe upstream side upper tank 321 and is integrally fixed to thedownstream side upper tank 311 and the upstream side upper tank 321 by,for example, brazing. The communication passage forming member 34A isplaced at the location, which projects laterally from the body of thecore 101. In the present embodiment, the communication passage formingmember 34A is configured into a box shape that projects laterally fromthe furthermost downstream side upper tank 311. Furthermore, thecommunication passage forming member 34A is made of the material that issimilar to or the same as that of the furthermost downstream side uppertank 311. In the evaporator of the present embodiment, a separator isnot provided in the downstream side upper tank 31. Therefore, thefurthermost downstream side upper tank 311 is the downstream side uppertank 31 itself.

With the above construction, a portion of the refrigerant in thefurthermost downstream side upper tank 311 is supplied into the firstcommunication passage 33A through the communication passage inlet 341 aand flows toward the upstream side of the air flow to enter thefurthermost upstream side upper tank 321 through the communicationpassage outlet 341 b. Then, this refrigerant in the furthermost upstreamside upper tank 321 flows downwardly through the furthermost upstreamside flow passage row 221 and then flows into the furthermost upstreamside lower tank 421, which is opposite from the furthermost upstreamside upper tank 321 in the top-to-bottom direction of the core. Theremaining refrigerant in the furthermost downstream side upper tank 311flows downwardly through the furthermost downstream side flow passagerow 211 and is supplied into the furthermost downstream side lower tank411, which is opposite from the furthermost downstream side upper tank311 in the top-to-bottom direction of the core. Then, this refrigerantflows toward the upstream side of the air flow and enters into theupstream side lower tank 421 where this refrigerant is merged with thebranched portion of the refrigerant, which has passed through the firstcommunication passage 33A.

Next, the flow of the refrigerant in the evaporator will be sequentiallydescribed. The refrigerant from the external constituent component ofthe refrigeration cycle is supplied into the downstream side lower tank41, which is the space on the left lateral side of the separator 41 a(the side of the separator 41 a, which is opposite from the X-direction)through the upper flow inlet 51 and the side flow passage 2. Then, therefrigerant flows upwardly through the downstream side flow passage row21 a (the first path) and is supplied into the downstream side uppertank 311.

Then, a portion of the refrigerant in the downstream side upper tank 311is branched into the first communication passage 33A. Then, in the firstcommunication passage 33A, the branched portion of the refrigerant flowsin the X-direction and then flows toward the upstream side of the airflow (the side opposite from the Z-direction), and thereafter thebranched portion of the refrigerant flows in the direction opposite fromthe X-direction and is supplied into the upstream side upper tank 321.Thereafter, this branched portion of the refrigerant flows downwardlythrough the furthermost upstream side flow passage row 221 (the secondpath, the full-path portion 201) into the upstream side lower tank 421.

In contrast, the remaining refrigerant in the downstream side upper tank311, which is other than the branched portion of the refrigerant, flowsdownwardly through the furthermost downstream side flow passage row 211(the second path, the full-path portion 201) and then flows from theinterior of the downstream side lower tank 411 toward the upstream sideof the air flow into the upstream side lower tank 421 through thecommunication holes 400 in the second communication passage 43. Then,this refrigerant is merged with the above branched portion of therefrigerant, which is supplied through the furthermost upstream sideflow passage row 221 after flowing downwardly therethrough, in theupstream side lower tank 421. That is, the refrigerant in thefurthermost downstream side flow passage row 211 and the refrigerant inthe furthermost upstream side flow passage row 221 flow downwardlyparallel to one another. The flow direction of the merged refrigerant,which is merged in the upstream side lower tank 421, is reversed, andthis refrigerant flows upwardly through the upstream side flow passagerow 22 a (the third path). Thereafter, this refrigerant flows to theoutside of the core from the upstream side upper tank 32 through theflow outlet 52.

In the evaporator of the present embodiment, the first communicationpassage 33A is placed at the location, which projects laterally from thebody of the core 101. The refrigerant, which has passed through themultiple downstream side flow passage rows 21 upwardly and downwardlymultiple turns in the S-shaped path, gets the inertial force and reachesthe furthermost downstream side upper tank 311. This refrigerant flowsthrough the first communication passage 33A (the upper communicationpassage), which is placed at the location that projects laterally fromthe body of the core 101. Thus, the refrigerant can get the additionalinertial force to promote the flow of the refrigerant toward theupstream side of the air flow, and thereby the refrigerant in thedownstream side upper tank 311 can be supplied in the greater amount tothe furthermost upstream side flow passage row 221.

Fifth Embodiment

The evaporator according to a fifth embodiment of the present inventionis a modification of the evaporator of the fourth embodiment and will bedescribed with reference to FIG. 9. FIG. 9 is a schematic diagramshowing the structure of the evaporator 1 and the flow of refrigeranttherein according to the present embodiment. In the present embodiment,the second communication passage 43 (the lower communication passage) ofthe evaporator is modified from that of the evaporator 1 of FIG. 8 in amanner similar to the first communication passage 33A. Thus, the secondcommunication passage 43 is placed at a location, which projectslaterally from the body of the core 101 in the X-direction (the lateraldirection). Other than this point, the evaporator of the presentembodiment is the same as the evaporator 1 of FIG. 8 and provides thesame effects and the same advantages as those of the evaporator 1 ofFIG. 8.

Sixth Embodiment

The evaporator according to a sixth embodiment of the present inventionis a modification of the evaporator of the fifth embodiment and will bedescribed with reference to FIGS. 10 and 11. FIG. 10 is a schematicdiagram showing the structure of the evaporator and the flow ofrefrigerant therein according to the present embodiment. FIG. 11 is aschematic diagram showing a positional relationship of the communicationpassage inlet 341 a and the communication passage outlet 341 b relativeto the downstream side flow passage row 211 and the upstream side flowpassage row 221.

The evaporator of the present embodiment is different from theevaporator of FIG. 9 with respect to the refrigerant flow pattern, thestructure of the core 102, the number of the downstream side flowpassage rows and the number of the upstream side flow passage rows. InFIG. 10, components similar to those of FIG. 9 will be indicated by thesame reference numerals. Other than the above points, the evaporator ofthe present embodiment is the same as the evaporator of FIG. 9 andprovides the same effects and the same advantages as those of theevaporator of FIG. 9.

The refrigerant flow pattern in the evaporator of the present embodimentis constructed from three downstream side flow passage rows and twoupstream side flow passage rows. The three downstream side flow passagerows include one downstream side flow passage row 21 b (the refrigerantdownflow portion), one downstream side flow passage row 21 a (therefrigerant upflow portion) and one furthermost downstream side flowpassage row 211 (the refrigerant downflow portion). The two upstreamside flow passage rows include one furthermost upstream side flowpassage row 221 (the refrigerant downflow portion) and one upstream sideflow passage row 22 a (the refrigerant upflow portion). Furthermore, theevaporator of the present embodiment does not have the side flowpassage.

In this instance, the number of the refrigerant flow paths is four.Furthermore, the refrigerant flow pattern in the evaporator is expressedby the number of path(s) in the downstream side flow passage rows 21,the number of path(s) in the upstream side flow passage row 22 and thenumber of path(s) of the full-path portion 201 (the portion where thebranched flow of the refrigerant from the downstream side to theupstream side flows downwardly). These numbers are written one afteranother according to the flow order of the refrigerant in the evaporator1 and are thereby expressed as a 2-1-1 refrigerant flow pattern in thisinstance.

With the above construction, a portion of the refrigerant in thefurthermost downstream side upper tank 311 is supplied into the firstcommunication passage 33A through the communication passage inlet 341 aand flows toward the upstream side of the air flow to enter thefurthermost upstream side upper tank 321 through the communicationpassage outlet 341 b. Then, this refrigerant in the furthermost upstreamside upper tank 321 flows downwardly through the furthermost upstreamside flow passage row 221 and then flows into the furthermost upstreamside lower tank 421, which is opposite from the furthermost upstreamside upper tank 321 in the top-to-bottom direction of the core. Theremaining refrigerant in the furthermost downstream side upper tank 311flows downwardly through the furthermost downstream side flow passagerow 211 and is supplied into the furthermost downstream side lower tank411, which is opposite from the furthermost downstream side upper tank311 in the top-to-bottom direction. Thereafter, this refrigerant flowsinto the second communication passage 43 through the communicationpassage inlet 441 a and flows toward the upstream side of the air flowin the second communication passage 43. Then, this refrigerant flowsinto the upstream side lower tank 421 through the communication passageoutlet 441 b. In the upstream side lower tank 421, this refrigerant ismerged with the branched portion of the refrigerant, which has passedthrough the first communication passage 33A.

Next, the flow of the refrigerant in the evaporator will be sequentiallydescribed. The refrigerant from the external constituent component ofthe refrigeration cycle is supplied into the downstream side upper tank31, which is the space on the left lateral side of the separator 31 a(the side of the separator 31 a, which is opposite from the X-direction)through the upper flow inlet 51. Then, the refrigerant flows downwardlythrough the downstream side flow passage row 21 b (the first path).Next, the flow direction of this refrigerant is reversed in the interiorof the downstream side lower tank 41, which is the space on the leftlateral side of the separator 41 a (the side of the separator 41 a,which is opposite from the X-direction), and thereafter the refrigerantflows upwardly through the downstream side flow passage row 21 a (thesecond path) and is supplied into the interior of the furthermostdownstream side upper tank 311.

Then, a portion of the refrigerant in the downstream side upper tank 311is branched into the first communication passage 33A. Then, in the firstcommunication passage 33A, the branched portion of the refrigerant flowsin the X-direction and then flows toward the upstream side of the airflow (the side opposite from the Z-direction), and thereafter thebranched portion of the refrigerant flows in the direction opposite fromthe X-direction and is supplied into the upstream side upper tank 321.Thereafter, this branched portion of the refrigerant flows downwardlythrough the furthermost upstream side flow passage row 221 (the thirdpath, the full-path portion 201) into the upstream side lower tank 421.

In contrast, the remaining refrigerant in the downstream side upper tank311, which is other than the branched portion of the refrigerant, flowsdownwardly through the furthermost downstream side flow passage row 211(the third path, the full-path portion 201) and then flows from theinterior of the downstream side lower tank 411 into the secondcommunication passage 43. Then, in the second communication passage 43,the refrigerant flows in the X-direction and then flows toward theupstream side of the air flow (the side opposite from the Z-direction),and thereafter the refrigerant flows in the direction opposite from theX-direction and is supplied into the upstream side lower tank 421 wherethis refrigerant is merged with the branched portion of the refrigerant,which has flown downwardly through the furthermost upstream side flowpassage row 221. That is, the refrigerant in the furthermost downstreamside flow passage row 211 and the refrigerant in the furthermostupstream side flow passage row 221 flow downwardly parallel to oneanother. The flow direction of the merged refrigerant, which is mergedin the upstream side lower tank 421, is reversed, and this refrigerantflows upwardly through the upstream side flow passage row 22 a (thefourth path). Thereafter, this refrigerant flows to the outside of thecore from the upstream side upper tank 32 through the flow outlet 52.

As shown in FIG. 11, the communication passage inlet 341 a (therefrigerant inflow opening) is opened to the interior of the furthermostdownstream side upper tank 311 and is located on an upper side of upperend openings 211 a of the tubes 20 a of the furthermost downstream sideflow passage row 211 in the vertical direction.

For the comparative purpose, it is now assumed that the refrigerant inthe furthermost flow passage row forms the downflow, and the refrigerantinflow opening of the first communication passage opens in thefurthermost downstream side upper tank only on a lower side of the upperend openings of the tubes of the furthermost flow passage row in thevertical direction. In such a case, the refrigerant tends to flow intothe furthermost downstream side flow passage row of the core, andthereby the refrigerant cannot easily flow into the first communicationpassage through the refrigerant inflow opening. With the above structureof the present embodiment, it is possible to limit the flow tendency ofthe refrigerant in the furthermost downstream side upper tank into thedownstream side flow passage row, and thereby it is possible to guidethe refrigerant into the communication passage inlet 341 a (therefrigerant inflow opening) and thereby to supply the greater amount ofthe refrigerant into the upstream side flow passage row. As a result,the heat exchange performance of the evaporator can be improved.

Furthermore, it is desirable that the lower end of the opening of thecommunication passage inlet 341 a (the refrigerant inflow opening) islocated on the upper side of the upper end openings 211 a of the tubes20 a of the furthermost downstream side flow passage row 211.

Furthermore, in the evaporator of the present embodiment, the number ofthe downstream side flow passage rows 21 and the number of the upstreamside flow passage rows 22 are set as follows. That is, the number of theother downstream side flow passage rows 21 a, 21 b other than thefurthermost downstream side flow passage row 211 is two, and the numberof the other upstream side flow passage row 22 a other than thefurthermost upstream side flow passage row 221 is one. Therefore, thenumber of the other downstream side flow passage rows 21 a, 21 b otherthan the furthermost downstream side flow passage row 211 is greaterthan the number of the other upstream side flow passage row 22 a otherthan the furthermost upstream side flow passage row 221. With the abovestructure, in the case of the heat exchanger, in which the dryness ofthe refrigerant is larger on the downstream side in comparison to theupstream side, it is possible to reduce the pressure loss.

Seventh Embodiment

The evaporator according to a seventh embodiment of the presentinvention is a modification of the evaporator of the sixth embodimentand will be described with reference to FIGS. 12 and 13. FIG. 12 is aschematic diagram showing the structure of the evaporator and the flowof refrigerant therein according to the present embodiment. FIG. 13 is aschematic diagram showing the positional relationship of thecommunication holes 300 relative to the downstream side flow passage row211 and the upstream side flow passage row 221. Although the downstreamside flow passage row 211 is not shown in FIG. 13, it should beunderstood that the downstream side flow passage row 211 is placed atthe same position in the Y-direction (the same vertical position), whichis the same as that of the upstream side flow passage row 221.

The evaporator of the present embodiment is the same as the evaporatorof FIG. 10 with respect to the refrigerant flow pattern and thestructure of the core 102 except that the communication passage formingmembers 34A, 44A are not provided separately from the rest of the core102 to project laterally. In FIG. 12, components similar to those ofFIG. 10 will be indicated by the same reference numerals. Other than theabove point, the evaporator of the present embodiment is the same as theevaporator of FIG. 10 and provides the same effects and the sameadvantages as those of the evaporator of FIG. 10.

With the above construction, a portion of the refrigerant in thefurthermost downstream side upper tank 311 flows through thecommunication holes 300 in the first communication passage 33 toward theupstream side of the air flow and is supplied into the upstream sideupper tank 321. Thereafter, this refrigerant flows downwardly throughthe furthermost upstream side flow passage row 221 and is supplied intothe upstream side lower tank 421, which is opposite from the furthermostupstream side upper tank 321 in the top-to-bottom direction of the core.The communication holes 300 also serve as a branching passage, which isprovided between the furthermost downstream side upper tank 311 and thefurthermost upstream side upper tank 321, so that a portion of therefrigerant in the furthermost downstream side upper tank 311 flowstoward the upstream side of the air flow and is supplied into theupstream side upper tank 321 through this branching passage.

In contrast, the remaining refrigerant in the furthermost downstreamside upper tank 311 flows downwardly through the furthermost downstreamside flow passage row 211 and is supplied into the furthermostdownstream side lower tank 411, which is opposite from the furthermostdownstream side upper tank 311. Then, this refrigerant flows toward theupstream side of the air flow through the communication holes 400 in thesecond communication passage 43 and is supplied into the upstream sidelower tank 421 where this refrigerant is merged with the branchedportion of the refrigerant, which has passed through the firstcommunication passage 33. The second communication passage 43, whichincludes the communication holes 400, also serves as a merging passage,which is provided between the furthermost downstream side lower tank 411and the furthermost upstream side lower tank 421, so that the remainingrefrigerant in the furthermost downstream side lower tank 411 flowstoward the upstream side of the air flow and is supplied into theupstream side lower tank 421 through the communication holes 400 in thesecond communication passage 43 to merge with the branched portion ofthe refrigerant at the interior of the upstream side lower tank 421.

The communication holes 300 are opened to the interior of thefurthermost downstream side upper tank 311, and the openings of thecommunication holes 300 are placed on an upper side of the upper endopenings 211 a of the tubes 20 a of the furthermost downstream side flowpassage row 211 and the upper end openings 221 a of the tubes 20 b ofthe furthermost upstream side flow passage row 221 in the verticaldirection.

For the comparative purpose, it is now assumed that the refrigerant inthe furthermost flow passage row forms the downflow, and thecommunication holes in the interior of the furthermost downstream sideupper tank, which are communicated with the interior of the upstreamside upper tank, open only on a lower side of the upper end openings ofthe tubes of the furthermost flow passage row in the vertical direction.In such a case, the refrigerant tends to flow into the furthermostdownstream side flow passage row of the core. With the above structureof the present embodiment, it is possible to limit the flow tendency ofthe refrigerant in the furthermost downstream side upper tank into thedownstream side flow passage row, and thereby it is possible to supplythe greater amount of the refrigerant into the upstream side flowpassage row. As a result, the heat exchange performance of theevaporator can be improved.

Furthermore, it is desirable that the lower ends of the openings of thecommunication holes 300 are located on the upper side of the upper endopenings 211 a of the tubes 20 a of the furthermost downstream side flowpassage row 211.

Eighth Embodiment

The evaporator according to an eighth embodiment of the presentinvention is a modification of the evaporator of FIG. 3 of the firstembodiment and will be described with reference to FIGS. 14 and 15. FIG.14 is a schematic diagram showing the structure of the evaporator andthe flow of refrigerant therein according to the present embodiment.FIG. 15 is a schematic diagram showing the positional relationship ofthe communication holes 400 relative to the downstream side flow passagerow 210 and the upstream side flow passage row 220. Although thedownstream side flow passage row 210 is not shown in FIG. 15, it shouldbe understood that the downstream side flow passage row 210 is placed atthe same position in the Y-direction (the same vertical position), whichis the same as that of the upstream side flow passage row 220.

The evaporator of the present embodiment is the same as the evaporatorof FIG. 3 with respect to the refrigerant flow pattern and the structureof the core except that the communication passage forming member 44 isnot provided separately from the rest of the core to project laterally.Here, the second communication passage 43 is formed between the interiorof the downstream side lower tank 411 and the interior of the upstreamside lower tank 421. In FIG. 14, components similar to those of FIG. 3will be indicated by the same reference numerals. Other than the abovepoint, the evaporator of the present embodiment is the same as theevaporator of FIG. 3 and provides the same effects and the sameadvantages as those of the evaporator of FIG. 3.

With the above construction, a portion of the refrigerant in thefurthermost downstream side lower tank 411 flows through thecommunication holes 400 in the second communication passage 43 towardthe upstream side of the air flow and is supplied into the upstream sidelower tank 421. Thereafter, this refrigerant flows upwardly through thefurthermost upstream side flow passage row 220 and is supplied into theupstream side upper tank 321, which is opposite from the furthermostupstream side lower tank 421 in the top-to-bottom direction of the core.The second communication passage 43, which includes the communicationholes 400, also serves as a branching passage, which is provided betweenthe furthermost downstream side lower tank 411 and the furthermostupstream side lower tank 421, so that a portion of the refrigerant inthe furthermost downstream side lower tank 411 flows toward the upstreamside of the air flow and is supplied into the upstream side lower tank421 through the communication holes 400 in the second communicationpassage 43.

In contrast, the remaining refrigerant in the furthermost downstreamside lower tank 411 flows upwardly through the furthermost downstreamside flow passage row 210 and is supplied into the furthermostdownstream side upper tank 311, which is opposite from the furthermostdownstream side lower tank 411 in the top-to-bottom direction of thecore. Then, this refrigerant flows toward the upstream side of the airflow through the communication holes 300 in the first communicationpassage 33 and is supplied into the upstream side upper tank 321 wherethis refrigerant is merged with the branched portion of the refrigerant,which has passed through the second communication passage 43. Thecommunication holes 300 also serve as a merging passage, which isprovided between the furthermost downstream side upper tank 311 and thefurthermost upstream side upper tank 321, so that the remainingrefrigerant in the furthermost downstream side upper tank 311 flowstoward the upstream side of the air flow and is supplied into theupstream side upper tank 321 through the communication holes 300 in thefirst communication passage 33 to merge with the branched portion of therefrigerant at the interior of the upstream side upper tank 321.

The communication holes 400 are opened to the interior of thefurthermost downstream side lower tank 411, and the openings of thecommunication holes 400 are placed on a lower side of the lower endopenings 210 a of the tubes 20 a of the furthermost downstream side flowpassage row 210 and the lower end openings 220 a of the tubes 20 b ofthe furthermost upstream side flow passage row 220 in the verticaldirection.

For the comparative purpose, it is now assumed that the refrigerant inthe furthermost flow passage row forms the upflow, and the communicationholes in the interior of the furthermost downstream side lower tank,which are communicated with the interior of the upstream side lowertank, open only on an upper side of the lower end openings of the tubesof the furthermost flow passage row in the vertical direction. In such acase, the refrigerant tends to flow into the furthermost downstream sideflow passage row of the core. With the above structure of the presentembodiment, it is possible to limit the flow tendency of the refrigerantin the furthermost downstream side lower tank into the downstream sideflow passage row, and thereby it is possible to supply the greateramount of the refrigerant into the upstream side flow passage row. As aresult, the heat exchange performance of the evaporator can be improved.

Furthermore, it is desirable that the lower ends of the openings of thecommunication holes 400 are located on the upper side of the lower endopenings 210 a of the tubes 20 a of the furthermost downstream side flowpassage row 210.

Ninth Embodiment

In a ninth embodiment of the present invention, a modification (a caseof six paths of refrigerant flow) of the evaporator of the eighthembodiment will be described with reference to FIG. 16. FIG. 16 is aschematic diagram showing the structure of the evaporator and the flowof refrigerant therein in the case where the number of the refrigerantflow paths is six.

The evaporator of the present embodiment is different from theevaporator of FIG. 14 with respect to the refrigerant flow pattern (sixpaths in this embodiment), the structure of the core 103 and theelimination of the side flow passage. Other than the above points, theevaporator of the present embodiment is the same as the evaporator ofFIG. 14 and provides the same effects and the same advantages as thoseof the evaporator of FIG. 14.

The refrigerant flow pattern in the evaporator of the present embodimentis constructed from four downstream side flow passage rows and threeupstream side flow passage rows. The four downstream side flow passagerows include two downstream side flow passage rows 21 b (the refrigerantdownflow portion), one downstream side flow passage row 21 a (therefrigerant upflow portion) and one furthermost downstream side flowpassage row 210 (the refrigerant upflow portion). The three upstreamside flow passage rows include one furthermost upstream side flowpassage row 220 (the refrigerant upflow portion), one upstream side flowpassage row 22 b (the refrigerant downflow portion) and one upstreamside flow passage row 22 a (the refrigerant upflow portion).

Therefore, the number of the refrigerant flow paths in the core 103 issix in the present embodiment. Furthermore, the refrigerant flow patternin the evaporator is expressed by the number of path(s) in thedownstream side flow passage rows 21, the number of path(s) in theupstream side flow passage row 22 and the number of path(s) of thefull-path portion 200 (the portion where the branched flow of therefrigerant from the downstream side to the upstream side flowsupwardly). These numbers are written one after another according to theflow order of the refrigerant in the evaporator and are therebyexpressed as a 3-1-2 refrigerant flow pattern in this instance.

Next, the flow of the refrigerant in the evaporator will be sequentiallydescribed. The refrigerant from the external constituent component ofthe refrigeration cycle is supplied into the downstream side upper tank31, which is the space on the left lateral side of the separator 31 a(the side of the separator 31 a, which is opposite from the X-direction)through the upper flow inlet 51. Then, the refrigerant flows downwardlythrough the downstream side flow passage row 21 b (the first path).Next, the flow direction of this refrigerant is reversed in the interiorof the downstream side lower tank 41, which is the space on the leftlateral side of the separator 41 a (the side of the separator 41 a,which is opposite from the X-direction), and thereafter the refrigerantflows upwardly through the downstream side flow passage row 21 a (thesecond path). Thereafter, this refrigerant is supplied into thedownstream side upper tank 31, which is the space between the separator31 b and the separator 31 a, and the flow direction of this refrigerantis reversed in the interior of the downstream side upper tank 31. Then,this refrigerant flows downward through the downstream side flow passagerow 21 b (the third path) and is supplied into the furthermostdownstream side lower tank 411.

A portion of the refrigerant in the downstream side lower tank 411 isbranched and flows toward the upstream side of the air flow (the sideopposite from the Z-direction) through the communication holes 400 inthe second communication passage 43. Then, this refrigerant is suppliedinto the upstream side lower tank 421. Then, this refrigerant flowsupwardly through the upstream side flow passage row 220 (the fourthpath, the full-path portion 200) and is supplied into the upstream sideupper tank 321.

In contrast, the remaining refrigerant in the downstream side lower tank411, which is other than the branched portion of the refrigerant, flowsupwardly through the furthermost downstream side flow passage row 210(the fourth path, the full-path portion 200) and then flows from theinterior of the downstream side upper tank 311 toward the upstream sideof the air flow into the upstream side upper tank 321 through thecommunication holes 300 in the first communication passage 33. Then,this refrigerant is merged with the above branched portion of therefrigerant, which is supplied through the furthermost upstream sideflow passage row 220 after flowing upwardly therethrough. That is, therefrigerant in the furthermost downstream side flow passage row 210 andthe refrigerant in the furthermost upstream side flow passage row 220flow upwardly parallel to one another.

The flow direction of the merged refrigerant, which is merged in theinterior of the upstream side upper tank 321, is reversed, and thisrefrigerant flows downwardly through the upstream side flow passage row22 b (the fifth path). Then, the flow direction of this refrigerant isreversed once again in the upstream side lower tank 42, and thereby therefrigerant flows upwardly through the upstream side flow passage row 22a (the sixth path). Thereafter, this refrigerant flows to the outside ofthe core from the upstream side upper tank 32 through the flow outlet52.

Furthermore, in the evaporator of the present embodiment, the number ofthe downstream side flow passage rows 21 and the number of the upstreamside flow passage rows 22 are set as follows. That is, the number of theother downstream side flow passage rows 21 a, 21 b other than thefurthermost downstream side flow passage row 210 is three, and thenumber of the other upstream side flow passage row 22 a, 22 b other thanthe furthermost upstream side flow passage row 220 is two. Therefore,the number of the other downstream side flow passage rows 21 a, 21 bother than the furthermost downstream side flow passage row 210 isgreater than the number of the other upstream side flow passage row 22a, 22 b other than the furthermost upstream side flow passage row 220.With the above structure, in the case of the heat exchanger, in whichthe dryness of the refrigerant is larger on the downstream side incomparison to the upstream side, it is possible to reduce the pressureloss.

Tenth Embodiment

In a tenth embodiment of the present invention, a modification (a caseof five paths of refrigerant flow) of the evaporator of the ninthembodiment will be described with reference to FIG. 17. FIG. 17 is aschematic diagram showing the structure of the evaporator and the flowof refrigerant therein in the case where the number of the refrigerantflow paths is five.

The evaporator of the present embodiment is different from theevaporator of FIG. 16 with respect to the refrigerant flow pattern (fivepaths in this embodiment) and the structure of the core 104 and thelocation of the flow inlet 51 (the lower side in this embodiment). Otherthan the above point, the evaporator of the present embodiment is thesame as the evaporator of FIG. 16 and provides the same effects and thesame advantages as those of the evaporator of FIG. 16.

The refrigerant flow pattern in the evaporator of the present embodimentis constructed from three downstream side flow passage rows and threeupstream side flow passage rows. The three downstream side flow passagerows include one downstream side flow passage row 21 a (the refrigerantupflow portion), one downstream side flow passage row 21 b (therefrigerant downflow portion) and one furthermost downstream side flowpassage row 210 (the refrigerant upflow portion). The three upstreamside flow passage rows include one furthermost upstream side flowpassage row 220 (the refrigerant upflow portion), one upstream side flowS passage row 22 b (the refrigerant downflow portion) and one upstreamside flow passage row 22 a (the refrigerant upflow portion).

Therefore, the number of the refrigerant flow paths in the core 100 isfive in the present embodiment. Furthermore, the refrigerant flowpattern in the evaporator is expressed by the number of path(s) in thedownstream side flow passage rows 21, the number of path(s) in theupstream side flow passage row 22 and the number of path(s) of thefull-path portion 200 (the portion where the branched flow of therefrigerant from the downstream side to the upstream side flowsupwardly). These numbers are written one after another according to theflow order of the refrigerant in the evaporator and are therebyexpressed as a 2-1-2 refrigerant flow pattern in this instance.

Next, the flow of the refrigerant in the evaporator will be sequentiallydescribed. The refrigerant from the external constituent component ofthe refrigeration cycle is supplied into the downstream side lower tank41, which is the space on the left lateral side of the separator 41 a(the side of the separator 41 a, which is opposite from the X-direction)through the lower flow inlet 51. Then, the refrigerant flows upwardlythrough the downstream side flow passage row 21 a (the first path).Next, the flow direction of this refrigerant is reversed in the interiorof the downstream side upper tank 31, which is the space on the leftlateral side of the separator 31 a (the side of the separator 31 a,which is opposite from the X-direction), and thereafter the refrigerantflows downwardly through the downstream side flow passage row 21 b (thesecond path). Thereafter, this refrigerant is supplied into the interiorof the furthermost downstream side lower tank 411.

A portion of the refrigerant in the downstream side lower tank 411 isbranched and flows toward the upstream side of the air flow (the sideopposite from the Z-direction) through the communication holes 400 inthe second communication passage 43. Then, this refrigerant is suppliedinto the upstream side lower tank 421. Then, this refrigerant flowsupwardly through the upstream side flow passage row 220 (the third path,the full-path portion 200) and is supplied into the upstream side uppertank 321.

In contrast, the remaining refrigerant in the downstream side lower tank411, which is other than the branched portion of the refrigerant, flowsupwardly through the furthermost downstream side flow passage row 210(the third path, the full-path portion 200) and then flows from theinterior of the downstream side upper tank 311 toward the upstream sideof the air flow into the upstream side upper tank 321 through thecommunication holes 300 in the first communication passage 33. Then,this refrigerant is merged with the above branched portion of therefrigerant, which is supplied through the furthermost upstream sideflow passage row 220 after flowing upwardly therethrough. That is, therefrigerant in the furthermost downstream side flow passage row 210 andthe refrigerant in the furthermost upstream side flow passage row 220flow upwardly parallel to one another.

The flow direction of the merged refrigerant, which is merged in theinterior of the upstream side upper tank 321, is reversed, and thisrefrigerant flows downwardly through the upstream side flow passage row22 b (the fourth path). Then, the flow direction of this refrigerant isreversed once again in the upstream side lower tank 42, and thereby therefrigerant flows upwardly through the upstream side flow passage row 22a (the fifth path). Thereafter, this refrigerant flows to the outside ofthe core from the upstream side upper tank 32 through the flow outlet52.

Eleventh Embodiment

An eleventh embodiment of the present invention is a modification (acase where the refrigerant flow pattern is 3-1-1 pattern) of theevaporator of the tenth embodiment and will be described with referenceto FIG. 18. FIG. 18 is a schematic diagram showing the structure of theevaporator and the refrigerant flow therethrough in the case where therefrigerant flow pattern is 3-1-1 according to the present embodiment.

In the evaporator of the present embodiment, the number of therefrigerant flow paths is five, which is the same as that of theevaporator of FIG. 17. However, the evaporator of the present embodimentis different from the evaporator of FIG. 17 with respect to therefrigerant flow pattern (3-1-1 pattern in the present embodiment) andthe flow direction of the refrigerant in the furthermost portion (therefrigerant downflow portion in this embodiment) of the core 105. Otherthan the above points, the evaporator of the present embodiment is thesame as the evaporator of FIG. 17 and provides the same effects and thesame advantages as those of the evaporator of FIG. 17.

The refrigerant flow pattern in the evaporator of the present embodimentis constructed from four downstream side flow passage rows and twoupstream side flow passage rows. The four downstream side flow passagerows include two downstream side flow passage rows 21 a (the refrigerantupflow portions), one downstream side flow passage row 21 b (therefrigerant downflow portion) and one furthermost downstream side flowpassage row 211 (the refrigerant downflow portion). The two upstreamside flow passage rows include one furthermost upstream side flowpassage row 221 (the refrigerant downflow portion) and one upstream sideflow passage row 22 a (the refrigerant upflow portion).

Therefore, the number of the refrigerant flow paths in the core 105 isfive in the present embodiment. Furthermore, the refrigerant flowpattern in the evaporator is expressed by the number of path(s) in thedownstream side flow passage rows 21, the number of path(s) in theupstream side flow passage row 22 and the number of path(s) of thefull-path portion 200 (the portion where the branched flow of therefrigerant from the downstream side to the upstream side flowsupwardly). These numbers are written one after another according to theflow order of the refrigerant in the evaporator and are therebyexpressed as a 3-1-1 refrigerant flow pattern in this instance.

Next, the flow of the refrigerant in the evaporator will be sequentiallydescribed. The refrigerant from the external constituent component ofthe refrigeration cycle is supplied into the downstream side lower tank41, which is the space on the left lateral side of the separator 41 a(the side of the separator 41 a, which is opposite from the X-direction)through the lower flow inlet 51. Then, the refrigerant flows upwardlythrough the downstream side flow passage row 21 a (the first path).Next, the flow direction of this refrigerant is reversed in the interiorof the downstream side upper tank 31, which is the space on the leftlateral side of the separator 31 a (the side of the separator 31 a,which is opposite from the X-direction), and thereafter the refrigerantflows downwardly through the downstream side flow passage row 21 b (thesecond path). Thereafter, the flow direction of this refrigerant isreversed in the interior of the downstream side lower tank 41, which isthe space defined between the separator 41 a and the separator 41 b.Then, this refrigerant flows upwardly through the downstream side flowpassage row 21 a (the third path) and is supplied into the interior ofthe furthermost downstream side upper tank 311.

A portion of the refrigerant in the downstream side upper tank 311 isbranched and flows toward the upstream side of the air flow (the sideopposite from the Z-direction) through the communication holes 300 inthe first communication passage 33. Then, this refrigerant is suppliedinto the upstream side upper tank 321. Then, this refrigerant flowsdownwardly through the upstream side flow passage row 221 (the fourthpath, the full-path portion 201) and is supplied into the upstream sidelower tank 421.

In contrast, the remaining refrigerant in the downstream side upper tank311, which is other than the branched portion of the refrigerant, flowsdownwardly through the furthermost downstream side flow passage row 211(the fourth path, the full-path portion 201) and then flows from theinterior of the downstream side lower tank 411 toward the upstream sideof the air flow into the upstream side lower tank 421 through thecommunication holes 400 in the second communication passage 43. Then,this refrigerant is merged with the above branched portion of therefrigerant, which is supplied through the furthermost upstream sideflow passage row 221 after flowing downwardly therethrough, in theupstream side lower tank 421. That is, the refrigerant in thefurthermost downstream side flow passage row 211 and the refrigerant inthe furthermost upstream side flow passage row 221 flow downwardlyparallel to one another.

Next, the flow direction of the merged refrigerant, which is merged inthe upstream side lower tank 421, is reversed, and this refrigerantflows upwardly through the upstream side flow passage row 22 a (thefifth path) and is supplied into the upstream side upper tank 32, whichis the space on the left lateral side of the separator 32 a (the side ofthe separator 32 a, which is opposite from the X-direction). Thereafter,this refrigerant flows to the outside of the core from the upstream sideupper tank 32 through the flow outlet 52.

Furthermore, in the evaporator of the present embodiment, the number ofthe downstream side flow passage rows 21 and the number of the upstreamside flow passage rows 22 are set as follows. That is, the number of theother downstream side flow passage rows 21 a, 21 b other than thefurthermost downstream side flow passage row 211 is three, and thenumber of the other upstream side flow passage row 22 a, 22 b other thanthe furthermost upstream side flow passage row 221 is one. Therefore,the number of the other downstream side flow passage rows 21 a, 21 bother than the furthermost downstream side flow passage row 211 isgreater than the number of the other upstream side flow passage row 22a, 22 b other than the furthermost upstream side flow passage row 221.With the above structure, in the case of the heat exchanger, in whichthe dryness of the refrigerant is larger on the downstream side incomparison to the upstream side, it is possible to reduce the pressureloss.

Twelfth Embodiment

In a twelfth embodiment of the present invention, a modification (a caseof four paths of refrigerant flow) of the evaporator of the eleventhembodiment will be described with reference to FIG. 19. FIG. 19 is aschematic diagram showing the structure of the evaporator and therefrigerant flow therethrough in the case where the refrigerant flowpattern is 2-1-1 according to the present embodiment.

The evaporator of the present embodiment is different from theevaporator of FIG. 18 with respect to the number of the paths (fourpaths in this embodiment) and the refrigerant flow patter (2-1-1 patternin this embodiment). Other than the above point, the evaporator of thepresent embodiment is the same as the evaporator of FIG. 18 and providesthe same effects and the same advantages as those of the evaporator ofFIG. 18.

The refrigerant flow pattern in the evaporator of the present embodimentis constructed from three downstream side flow passage rows and twoupstream side flow passage rows. The three downstream side flow passagerows include one downstream side flow passage row 21 b (the refrigerantdownflow portion), one downstream side flow passage row 21 a (therefrigerant upflow portion) and one furthermost downstream side flowpassage row 211 (the refrigerant downflow portion). The two upstreamside flow passage rows include one furthermost upstream side flowpassage row 221 (the refrigerant downflow portion) and one upstream sideflow passage row 22 a (the refrigerant upflow portion).

Therefore, the number of the refrigerant flow paths in the core 102 isfour in the present embodiment. Furthermore, the refrigerant flowpattern in the evaporator is expressed by the number of path(s) in thedownstream side flow passage rows 21, the number of path(s) in theupstream side flow passage row 22 and the number of path(s) of thefull-path portion 201 (the portion where the branched flow of therefrigerant from the downstream side to the upstream side flowsdownwardly). These numbers are written one after another according tothe flow order of the refrigerant in the evaporator and are therebyexpressed as a 2-1-1 refrigerant flow pattern in this instance.

Next, the flow of the refrigerant in the evaporator will be sequentiallydescribed. The refrigerant from the external constituent component ofthe refrigeration cycle is supplied into the downstream side upper tank31, which is the space on the left lateral side of the separator 31 a(the side of the separator 31 a, which is opposite from the X-direction)through the upper flow inlet 51. Then, the refrigerant flows downwardlythrough the downstream side flow passage row 21 b (the first path).Next, the flow direction of this refrigerant is reversed in the interiorof the downstream side lower tank 41, which is the space on the leftlateral side of the separator 41 a (the side of the separator 41 a,which is opposite from the X-direction), and thereafter the refrigerantflows upwardly through the downstream side flow passage row 21 a (thesecond path) and is supplied into the interior of the furthermostdownstream side upper tank 311.

A portion of the refrigerant in the downstream side upper tank 311 isbranched and flows toward the upstream side of the air flow (the sideopposite from the Z-direction) through the communication holes 300 inthe first communication passage 33. Then, this refrigerant is suppliedinto the upstream side upper tank 321. Then, this refrigerant flowsdownwardly through the furthermost upstream side flow passage row 221(the third path, the full-path portion 201) and is supplied into theupstream side lower tank 421.

In contrast, the remaining refrigerant in the downstream side upper tank311, which is other than the branched portion of the refrigerant, flowsdownward through the furthermost downstream side flow passage row 211(the third path, the full-path portion 201) and then flows from theinterior of the downstream side lower tank 411 toward the upstream sideof the air flow into the upstream side lower tank 421 through thecommunication holes 400 in the second communication passage 43. Then,this refrigerant is merged with the above branched portion of therefrigerant, which is supplied through the furthermost upstream sideflow passage row 221 after flowing downwardly therethrough, in theupstream side lower tank 421. That is, the refrigerant in thefurthermost downstream side flow passage row 211 and the refrigerant inthe furthermost upstream side flow passage row 221 flow downwardlyparallel to one another.

Next, the flow direction of the merged refrigerant, which is merged inthe upstream side lower tank 421, is reversed, and this refrigerantflows upwardly through the upstream side flow passage row 22 a (thefourth path) and is supplied into the upstream side upper tank 32, whichis the space on the left lateral side (the side of the separator 32 a,which is opposite from the X-direction). Thereafter, this refrigerantflows to the outside of the core from the upstream side upper tank 32through the flow outlet 52.

Thirteenth Embodiment

In a thirteenth embodiment of the present invention, a modification (acase of three paths of refrigerant flow) of the evaporator of thetwelfth embodiment will be described with reference to FIG. 20. FIG. 20is a schematic diagram showing the structure of the evaporator and therefrigerant flow therethrough in the case where the refrigerant flowpattern is 1-1-1 according to the present embodiment.

The evaporator of the present embodiment is different from theevaporator of FIG. 19 with respect to the structure of the core 106, thenumber of refrigerant flow paths (three in this embodiment), therefrigerant flow pattern (1-1-1 pattern in this embodiment) and thelocation of the flow inlet 51 (lower side in this embodiment). Otherthan the above points, the evaporator of the present embodiment is thesame as the evaporator of FIG. 19 and provides the same effects and thesame advantages as those of the evaporator of FIG. 19.

The refrigerant flow pattern in the evaporator 1 of the presentembodiment is constructed from two downstream side flow passage rows andtwo upstream side flow passage rows. The two downstream side flowpassage rows include one downstream side flow passage row 21 a (therefrigerant upflow portion) and one furthermost downstream side flowpassage row 211 (the refrigerant downflow portion). The two upstreamside flow passage rows include one furthermost upstream side flowpassage row 221 (the refrigerant downflow portion) and one upstream sideflow passage row 22 a (the refrigerant upflow portion).

Therefore, the number of the refrigerant flow paths in the core 106 isthree in the present embodiment. Furthermore, the refrigerant flowpattern in the evaporator is expressed by the number of path(s) in thedownstream side flow passage rows 21, the number of path(s) in theupstream side flow passage row 22 and the number of path(s) of thefull-path portion 201 (the portion where the branched flow of therefrigerant from the downstream side to the upstream side flowsdownwardly). These numbers are written one after another according tothe flow order of the refrigerant in the evaporator and are therebyexpressed as a 1-1-1 refrigerant flow pattern in this instance.

Next, the flow of the refrigerant in the evaporator will be sequentiallydescribed. The refrigerant from the external constituent component ofthe refrigeration cycle is supplied into the interior of the downstreamside lower tank 41, which is the space on the left lateral side of theseparator 41 a (the side of the separator 41 a, which is opposite fromthe X-direction) through the lower flow inlet 51. Then, the refrigerantflows upwardly through the downstream side flow passage row 21 a (thefirst path) and is supplied into the downstream side upper tank 311.

A portion of the refrigerant in the downstream side upper tank 311 isbranched and flows toward the upstream side of the air flow (the sideopposite from the Z-direction) through the communication holes 300 inthe first communication passage 33. Then, this refrigerant is suppliedinto the upstream side upper tank 321. Then, this refrigerant flowsdownwardly through the upstream side flow passage row 221 (the secondpath, the full-path portion 201) and is supplied into the upstream sidelower tank 421.

In contrast, the remaining refrigerant in the downstream side upper tank311, which is other than the branched portion of the refrigerant, flowsdownwardly through the furthermost downstream side flow passage row 211(the second path, the full-path portion 201) and then flows from theinterior of the downstream side lower tank 411 toward the upstream sideof the air flow into the upstream side lower tank 421 through thecommunication holes 400 in the second communication passage 43. Then,this refrigerant is merged with the above branched portion of therefrigerant, which is supplied through the furthermost upstream sideflow passage row 221 after flowing downwardly therethrough, in theupstream side lower tank 421. That is, the refrigerant in thefurthermost downstream side flow passage row 211 and the refrigerant inthe furthermost upstream side flow passage row 221 flow downwardlyparallel to one another.

Next, the flow direction of the merged refrigerant, which is merged inthe upstream side lower tank 421, is reversed, and this refrigerantflows upwardly through the upstream side flow passage row 22 a (thethird path) and is supplied into the upstream side upper tank 32, whichis the space on the left lateral side of the separator 32 a (the side ofthe separator 32 a, which is opposite from the X-direction). Thereafter,this refrigerant flows to the outside of the core from the upstream sideupper tank 32 through the flow outlet 52.

Fourteenth Embodiment

In a fourteenth embodiment of the present invention, the positioningstate of the evaporator (the state where the core is tilted relative tothe horizontal direction), which is applicable to all of the embodimentsof the present invention, will be described with reference to FIG. 21.FIG. 21 is a schematic side view of the positioning state of theevaporator according to the present embodiment. FIG. 22 is an enlargedpartial cross sectional side view showing the relationship between theinterior of the upper header tank 3 and the refrigerant quantities (therefrigerant quantity in the upstream side and the refrigerant quantityin the downstream side) in the core 100 at the furthermost portionthereof. FIG. 23 is an enlarged partial cross sectional side viewshowing the relationship between the interior of the lower header tank 4and the refrigerant quantities (the refrigerant quantity in the upstreamside and the refrigerant quantity in the downstream side) in the core100 at the furthermost portion thereof.

With reference to FIG. 21, the core 100 has an upstream side lateralcore surface (upstream side lateral plane) 100 b and a downstream sidelateral core surface (downstream side lateral plane) 100 a, which aregenerally parallel to each other and are located on the upstream sideand the downstream side, respectively, in the air flow direction. Theevaporator of the present embodiment is tilted such that the upstreamside lateral core surface 100 b of the core 100 is closer to animaginary horizontal plane L indicated by a dot-dash line in FIG. 21 (aplane that is placed vertically below the upstream side lower tank 42and is parallel to the Z-direction) in comparison to the downstream sidelateral core surface 100 a of the core 100. The core 100 is placed andis held at a tilt angle (specifically, a tilt angle of the upstream sidelateral core surface 100 b) θ relative to the imaginary horizontal plane(the imaginary horizontal line) L. Other than this point, the evaporatorof the present embodiment is the same as the evaporator 1 of the firstembodiment and provides the same effects and the same advantages asthose of the evaporator 1 of the first embodiment.

With this structure, due to the aid of the gravity, a portion of therefrigerant in the furthermost downstream side header tank 11 (e.g., thefurthermost downstream side upper tank 311 in the case of FIG. 22 andthe furthermost downstream side lower tank 411 in the case of FIG. 23)flows in the greater amount in comparison to the first embodimentthrough the communicating means (the first communication passage 33 or33A in the case of FIG. 22 and the second communication passage 43 or43A in the case of FIG. 23) toward the upstream side of the air flow andis supplied into the furthermost upstream side header tank 12 (e.g., thefurthermost upstream side upper tank 321 in the case of FIG. 22 and thefurthermost upstream side lower tank 421 in the case of FIG. 23). Atthis time, the refrigerant is under the influence of the gravity, sothat the refrigerant tends to flow through the communicating meanstoward the upstream side flow passage row 220, 221 rather than thefurthermost downstream side flow passage row 210, 211 due to the factthat the upstream side flow passage row 220, 221 is placed at the lowerside of the furthermost downstream side flow passage row 210, 211 in thevertical direction. Furthermore, the portion of the refrigerant, whichis supplied into the upstream side header tank 12 (e.g., the furthermostupstream side upper tank 321 in the case of FIG. 22 and the upstreamside lower tank 421 in the case of FIG. 23) flows through thefurthermost upstream side flow passage row 220, 221 toward the oppositeupstream side header tank 12 (e.g., the furthermost upstream side lowertank 421 in the case of FIG. 22 and the furthermost upstream side uppertank 321 in the case of FIG. 23), which is opposite from the aboveupstream side header tank 12 (e.g., the furthermost upstream side uppertank 321 in the case of FIG. 22 and the upstream side lower tank 421 inthe case of FIG. 23) in the top-to-bottom direction of the core 100.

In contrast, the rest of the refrigerant, which remains in thefurthermost downstream side header tank 11 (e.g., the furthermostdownstream side upper tank 311 in the case of FIG. 22 and thefurthermost downstream side lower tank 411 in the case of FIG. 23) flowsthrough the furthermost downstream side flow passage row 210, 211 towardthe opposite furthermost downstream side header tank 11 (e.g., thefurthermost downstream side lower tank 411 in the case of FIG. 22 andthe furthermost downstream side upper tank 311 in the case of FIG. 23),which is opposite from the above downstream side header tank 11 (e.g.,the furthermost downstream side upper tank 311 in the case of FIG. 22and the furthermost downstream side lower tank 411 in the case of FIG.23) in the top-to-bottom direction of the core 100. Then, thisrefrigerant flows toward the upstream side of the air flow into theupstream side header tank 12 (e.g., the furthermost upstream side lowertank 421 in the case of FIG. 22 and the upstream side upper tank 321 inthe case of FIG. 23) where this refrigerant is merged with the branchedportion of the refrigerant, which has passed through the communicatingmeans.

At the evaporator of the present embodiment, in the case where thefurthermost flow passage rows (the furthermost upstream side anddownstream side flow passage rows) form the refrigerant downflowportions (the full-path portion 201), the quantity of the refrigerant,which flows through the furthermost upstream side flow passage row 221,becomes greater than the quantity of the refrigerant, which flowsthrough the furthermost downstream side flow passage row 211 (see FIG.22). Furthermore, in the case where the furthermost flow passage rowsform the refrigerant upflow portions (the full-path portion 200), thequantity of the refrigerant, which flows through the furthermostupstream side flow passage row 220, becomes larger than the quantity ofthe refrigerant, which flows through the furthermost downstream sideflow passage row 210 (see FIG. 23).

In the evaporator of the present embodiment, the furthermost upstreamside flow passage row 220, 221 is placed on the lower side of thefurthermost downstream side flow passage row 210, 211, so that therefrigerant in the downstream side header tank 11 tends to flow towardthe furthermost upstream side flow passage row 220, 221 due to thegravity. Therefore, it is possible to alleviate the biased flow of therefrigerant, which tends to flow toward the downstream side flow passagerow at the furthermost portion of the core that is furthermost from theflow inlet 51 and the flow outlet 52.

Also, in the evaporator, the refrigerant of the gas phase and liquidphase mixture is supplied into the downstream side header tank 11. Theliquid phase refrigerant is heavier than the gas phase refrigerant.Thus, in addition to the inertial force, the gravity has the significantinfluence on the liquid phase refrigerant. Therefore, the liquid phaserefrigerant is expected to flow toward the upstream side flow passagerow 220, 221, which is placed on the lower side of the downstream sideflow passage row 210, 211. Thereby, the refrigerant can be more activelysupplied to the upstream side where the temperature of the blown air isrelatively high, so that the heat exchange performance can be furtherimproved.

Fifteenth Embodiment

In a fifteenth embodiment of the present invention, the structure of theheader tank, which is applicable to the evaporator of all of theembodiments of the present invention, will be described with referenceto FIGS. 24 to 26. FIG. 24 is a partial side view showing the upperheader tank 3 of the evaporator of the present embodiment. FIG. 25 is apartial cross sectional front view showing the flow inlet 51 of theupper header tank 3 of FIG. 24 seen from the X-direction in FIG. 24.FIG. 26 is a diagram (graph) showing a computed result of a relationshipbetween a tank outer diameter (a total tank outer diameter of theupstream side and downstream side header tanks or a total thickness ofthe upstream side and downstream side header tanks in the air flowdirection) D and a pressure loss in the tank obtained under apredetermined condition.

As shown in FIGS. 24 and 25, the upper header tank 3 and the tubes 20are formed from a plurality of plate members (constituent members) 50,which are integrally stacked and joined one after another in the lateraldirection. The plate member 50 has a through hole and an extendingportion. The extending portion of the plate member 50 extends from thethrough hole of the plate member 50 in the direction opposite from theY-direction. One side of the through hole of the plate member 50 isconfigured into a plate form, and the other side of the through hole ofthe plate member 50 is configured into a tubular form. The upper headertank 3 is formed by alternately directing and stacking the plate members50 of the above configuration, so that the tubular portion, whichextends in the X-direction, and the flow passages, which conduct therefrigerant, are created. Furthermore, it should be noted that althoughnot show in the drawing, the lower header tank 4 is also formed at theundepicted lower ends of the tubes 20 in FIG. 24 in a manner similar tothat of the upper header tank 3.

The above tubular portion, which extends in the X-direction, constitutesthe tank, and the lateral side end opening of the tubular portion can beused as the flow inlet 51 or the flow outlet 52. When the lateral sideend opening of the tubular portion is not used as the flow inlet 51 orthe flow outlet 52, the cap is fitted into the lateral side end openingto close the same. The tank interior (the tube interior) is communicatedwith the flow passages (the interiors of the tubes), which extend in thedirection opposite from the Y-direction.

FIG. 26 shows the relationship between the tank outer diameter or thethickness D (mm) and the pressure loss (kPa) in the case of the separatetype tank (indicated by a solid line) where separate tubes are joined tothe tank. FIG. 26 also shows the relationship between the tank outerdiameter D (mm) and the pressure loss (kPa) in the case of the laminatetype tank (indicated by a dotted line) where the plate members 50 arestacked. The tank outer diameter D is defined by the following equation1.

D=2(d+2t)   Equation 1

Here, “t” denotes a wall thickness of the tank. Furthermore, “d” denotesan equivalent inner diameter of the interior of the tank, which isobtained as follows. That is, first, an effective cross sectional areaof the interior of the tank is multiplied by 4, and then the thusobtained value (i.e., the product of the effective cross sectional areamultiplied by 4) is divided by a circumferential length of the interiorof the tank to obtain the equivalent inner diameter of the interior ofthe tank.

Furthermore, in the case of the separate type tank, the data of FIG. 26is computed for the corresponding predetermined condition where the wallthickness t of the tank is 1.0 mm (i.e., t=1.0 mm), and a protrusion ofthe tube into the interior of the tank is minimum of 4 mm. In the caseof the laminate type tank, the data of FIG. 26 is computed for thecorresponding predetermined condition where the wall thickness t of thetank is 1.0 mm (i.e., t=1.0 mm), and the tank brazing area is 1.5 to 3.0mm.

In the result of the computation of the above separate type tank and ofthe laminate type tank, the pressure loss factors are compared by usinga square of an inverse (a flow velocity factor) of the effective crosssectional area of the interior of the tank. Furthermore, the comparisonis made by using the pressure loss factor in the case of the tank outerdiameter D=70 mm as a reference.

As shown in FIG. 26, according to the result of the computation, it isdesirable that the thickness D of the both header tanks (the upstreamside and downstream side header tanks), which is measured in the airflow direction, is 48 mm or less. In this case, the tank interior spaceis not large, and thereby the pressure loss in the tank tends to becomelarge. Here, when the present invention is applied to the evaporator,which satisfies the above condition, the more prominent effect forreducing the pressure loss can be expected.

Sixteenth Embodiment

In a sixteenth embodiment of the present invention, an appropriaterelationship between a total passage cross sectional area S1 of thebranching passage and a total passage cross sectional area S2 of themerging passage, which is applicable to all of the embodiments of thepresent invention, will be described with reference to FIGS. 27 and 28.FIG. 27 is a schematic diagram for designing the appropriate conditionof the flow quantity (hereinafter, also referred to as the upstream siderefrigerant flow quantity) GR2 of the refrigerant, which flows in theupstream side flow passage row, and the flow quantity (hereinafter, alsoreferred to as the downstream side refrigerant flow quantity) GR1 of therefrigerant, which flows in the downstream side flow passage row. FIG.28 is a diagram showing the result of the computation of an appropriateratio (S1/S2) between the total passage cross sectional area S1 of thebranching passage and the total passage cross sectional area S2 of themerging passage computed for each corresponding one of the refrigerantflow paths (3 paths to 6 paths).

As shown in FIG. 27, in the case where the furthermost downstream sideflow passage row and the furthermost upstream side flow passage row arerefrigerant upflow portions, respectively, the flow quantity of therefrigerant flowing through the furthermost downstream side flow passagerow is indicated by “GR1”, and the flow quantity of the refrigerantflowing through the furthermost upstream side flow passage row isindicated by “GR2”. Furthermore, the flow quantity of the refrigerantflowing from the furthermost downstream side upper tank 311 to thefurthermost upstream side upper tank 321 is indicated by “GRU”, and theflow quantity of the refrigerant flowing from the furthermost downstreamside lower tank 411 to the furthermost upstream side lower tank 421 isindicated by “GRL”.

Furthermore, the number of the refrigerant flow paths in the core isindicated by “N”. At the second communication passage 43 or 43A (thebranching passage), which conducts the portion of the refrigerant fromthe furthermost downstream side lower tank 411 to the furthermostupstream side lower tank 421, the pressure loss is indicated by “ΔPt1”,and the dryness is indicated by “X1”. Also, the specific volume at thesecond communication passage 43 is indicated by “V1”. In addition, atthe first communication passage 33 or 33A (the merging passage), whichconducts the remaining refrigerant from the downstream side upper tank311 to the upstream side upper tank 321 after the remaining refrigerantbeing supplied from the furthermost downstream side lower tank 411 tothe furthermost downstream side upper tank 311 through the furthermostdownstream side flow passage row 210, the pressure loss is indicated by“ΔPt2”, and the dryness is indicated by “X2”. Also, the specific volumeat the first communication passage 33 is indicated by “V2”.

In comparison between the upstream side portion (the upstream side flowpassage row) of the core and the downstream side portion (the downstreamside flow passage row) of the core, which are placed one after anotherin the flow direction of the air, the air around the upstream sideportion of the core is warmer. Therefore, the upstream side portion ofthe core should have the higher performance. In a typical condition (anideal condition), the good balance of the performance is achieved withthe following state. That is, the air to be supplied to the core has thetemperature of 27° C. and the relative humidity of 50% RH. Furthermore,the air right after passing through the upstream side portion (theupstream side flow passage row) of the core has the temperature of 14°C. and the relative humidity of 85% RH, and the air right after passingthrough the downstream side portion (the downstream side flow passagerow) of the core has the temperature of 7° C. and the relative humidityof 90% RH.

When the amount of energy is computed for the above state, the ratiobetween the downstream side refrigerant flow quantity GR1 and theupstream side refrigerant flow quantity GR2 is 4:6. The above balancemay vary about ±10% due to the variation in the distribution of therefrigerant in the lateral direction (the width direction) of the core.In view of the above fact, it is desirable to set the ratio of GR1/GR2to be equal to or greater than 0.55 (=3.6/6.6) but is equal to or lessthan 0.81 (=4.4/5.4), i.e., 0.55≦GR1/GR2≦0.81.

Next, the result (see FIG. 28) of the computation of the appropriateratio (S1/S2) between the total passage cross sectional area S1 of thebranching passage and the total passage cross sectional area S2 of themerging passage will be described in view of the number of therefrigerant flow paths of the evaporator.

The logic of the computation will now be described. First, it should beunderstood that the dryness of the refrigerant before entering the corediffers from the dryness of the refrigerant after exiting the core. Inview of this fact, when the pressure loss ΔPt1 of the branching passageis set to be smaller than the pressure loss ΔPt2 of the merging passage(i.e., ΔPt1<ΔPt2), the refrigerant flow quantity of the downstream sideand the refrigerant flow quantity of the upstream side can be balanced.

The refrigerant flow quantity balance and the pressure loss depend onthe square of the flow velocity of the refrigerant, so that it isdesirable to satisfy the following equation 2.

S1/S2=(V1/V2)²   Equation 2

Furthermore, it is desirable that the refrigerant flow quantity in theupstream side portion of the core is larger than the refrigerant flowquantity in the downstream side portion of the core. Thus, it isdesirable to have the value of S1/S2, which is equal to or larger thanthe corresponding value shown in the column of “ANSWER” in FIG. 28.

As indicated in FIG. 28, it is desirable that the heat exchanger isconstructed to satisfy a condition of 0.41≦S1/S2. Furthermore, asdiscussed above, in the case where the furthermost downstream side flowpassage row and the furthermost upstream side flow passage row arerefrigerant upflow portions, respectively, the total passage crosssectional area S1 of the branching passage is the total passage crosssectional area S1 of the second communication passage 43, and the totalpassage cross sectional area S2 of the merging passage is the totalpassage cross sectional area S2 of the first communication passage 33.Furthermore, in a case where the second communication passage 43includes a plurality of sub-passages, the total passage cross sectionalarea S1 is a sum of all of cross sectional areas of the sub-passages ofthe second communication passage 43. Similarly, in a case where thefirst communication passage 33 includes a plurality of sub-passages, thetotal passage cross sectional area S2 is a sum of all of cross sectionalareas of the sub-passages of the first communication passage 33. Also,in a case where the second communication passage 43 is made of a singlepassage, the total passage cross sectional area S1 is the crosssectional area of this single passage. Similarly, in a case where firstcommunication passage 33 is made of a single passage, the total passagecross sectional area S2 is the cross sectional area of this singlepassage.

In contrast, in the case where the furthermost downstream side flowpassage row and the furthermost upstream side flow passage row arerefrigerant downflow portions, respectively, the total passage crosssectional area S1 of the branching passage is the total passage crosssectional area S1 of the first communication passage 33, and the totalpassage cross sectional area S2 of the merging passage is the totalpassage cross sectional area S2 of the second communication passage 43.Furthermore, in a case where the first communication passage 33 includesa plurality of sub-passages, the total passage cross sectional area Siis a sum of all of cross sectional areas of the sub-passages of thefirst communication passage 33. Similarly, in a case where the secondcommunication passage 43 includes a plurality of sub-passages, the totalpassage cross sectional area S2 is a sum of all of cross sectional areasof the sub-passages of the second communication passage 43. Also, in acase where the first communication passage 33 is made of a singlepassage, the total passage cross sectional area S1 is the crosssectional area of this single passage. Similarly, in a case where secondcommunication passage 43 is made of a single passage, the total passagecross sectional area S2 is the cross sectional area of this singlepassage.

In addition, as shown in FIG. 28, in the case where the number of therefrigerant flow paths in the core is six, it is desirable to satisfythe condition of 0.71≦S1/S2. Furthermore, in the case where the numberof the refrigerant flow paths in the core is five, it is desirable tosatisfy the relationship of 0.47≦S1/S2. Furthermore, in the case wherethe number of the refrigerant flow paths in the core is four, it isdesirable to satisfy the relationship of 0.66≦S1/S2. In addition, in thecase where the number of the refrigerant flow paths in the core isthree, it is desirable to satisfy the relationship of 0.41≦S1/S2.

Seventeenth Embodiment

In a seventeenth embodiment of the present invention, cores, in whichthe lateral size (lateral extension) of the furthermost upstream sideflow passage row 220, 221 and the lateral size (lateral extension) ofthe furthermost downstream side flow passage row 210, 211 measured inthe X-direction (lateral direction of the core) are not identical, willbe described with reference to FIGS. 29 and 30. FIG. 30 is a schematicdiagram showing a variation of the evaporator of FIG. 29 along with thestructure and the refrigerant flow thereof. Here, it should be notedthat although FIGS. 29 and 30 do not show the communication passageforming member(s) 34, 44 of the first to sixth embodiments, the presentembodiment is equally applicable to the evaporator of any one of thefirst to sixth embodiments with the communication passage formingmember(s) 34, 44. In other words, FIGS. 29 and 30 are only for thepurpose of showing the difference between the lateral size (lateralextension) of the furthermost upstream side flow passage row 220, 221and the lateral size (lateral extension) of the furthermost downstreamside flow passage row 210, 211.

FIG. 29 is a schematic diagram showing the structure and the refrigerantflow in the case of the evaporator, in which the lateral size of thefurthermost upstream side flow passage row 221 is larger than thelateral size of the furthermost downstream side flow passage row 211.Furthermore, in this evaporator, the furthermost downstream side flowpassage row and the furthermost upstream side flow passage row are therefrigerant downflow portions, respectively, and the refrigerant flowpattern is a 1-1-1 refrigerant flow pattern. In addition, the number ofthe refrigerant flow paths is three.

Next, FIG. 30 is the schematic diagram showing the structure and therefrigerant flow in the case of the evaporator, in which the lateralsize of the furthermost downstream side flow passage row 211 is largerthan the lateral size of the furthermost upstream side flow passage row221. Furthermore, in this evaporator, the furthermost downstream sideflow passage row and the furthermost upstream side flow passage row arethe refrigerant downflow portions, respectively, and the refrigerantflow pattern is a 1-1-1 refrigerant flow pattern. In addition, thenumber of the refrigerant flow paths is three.

Eighteenth Embodiment

In an eighteenth embodiment of the present invention, a positionalrelationship between the communication passage forming member and thecore, which is applicable to all of the embodiments of the presentinvention, will be described with reference to FIGS. 31 to 33. FIG. 31is a partial schematic front view showing the relationship between thecommunication passage forming member 44 and the core. FIG. 32 is apartial schematic front view showing the relationship between thecommunication passage forming member 44 and the core in a modificationof FIG. 31. FIG. 33 is a partial schematic front view showing therelationship between the communication passage forming member 44 and thecore in a further modification of the FIG. 31.

As shown in FIGS. 31 to 33, the communication passage forming member 44is provided such that at least a portion of the communication passageforming member 44 is placed laterally inward (on the left side in FIGS.31-33) of the lateral end of the core 100. With this construction, adead space can be reduced to reduce the lateral size of the core.

In FIG. 31, a longitudinal end portion of the side plate 500, whichsupports the core, is inserted into the interior of the communicationpassage forming member 44. Alternatively, a longitudinal end portion ofthe lateral end tube 20 a, which is located at the lateral ends of thecore, may be inserted into the interior of the communication passageforming member 44. With this construction, even in the case where theportion of the communication passage forming member 44 is placedlaterally inward of the lateral end of the core, it is not required tomake any particular adjustment of the longitudinal end portion of thetube 20 a or of the side plate 500. Thus, the manufacturing of the heatexchanger can be simplified.

In FIG. 32, a longitudinal end portion of the side plate 500, whichsupports the core, is bent and is inserted into the interior of thedownstream side lower tank 411. Alternatively, a longitudinal endportion of the tube 20 a, which is located at the lateral end of thecore, may be bent and inserted into the interior of the downstream sidelower tank 411. With this construction, even in the case where theportion of the communication passage forming member 44 is placedlaterally inward of the lateral ends of the core, the longitudinal endportion of the tube 20 a or of the side plate 500 is not placed at thesecond communication passage 43. Therefore, it is possible to reduce theflow resistance of the refrigerant in the communication passage.

FIG. 33 shows the evaporator, which has the tube 20 a, which is placedat the lateral end of the core and does not conduct the refrigeranttherethrough. The tube 20 a or the side plate 500, which supports thecore, has the longitudinal end portion, which is bent and contacts theouter surface of the communication passage forming member 44. With thisconstruction, even in the case where the portion of the communicationpassage forming member 44 is placed laterally inward of the lateral endsof the core, it is possible to eliminate the need for inserting thelongitudinal end portion of the tube 20 a or of the side plate 500 intothe interior of the tank.

Now, modifications of the above embodiments will be described.

In the above embodiments, the number of the flow passage rows in thedirection of the air flow (the Z-direction) is set to be two. However,the present invention is not limited to this. For example, the number ofthe flow passage rows in the direction of the air flow (the Z-direction)may be alternatively set to be three or more.

Furthermore, the core of the above embodiments may be modified such thatthe outer fins between the tubes may be eliminated from the core.Furthermore, the core of the above embodiments may be modified such thatprojections are created (for example by cutting) and bent at the tubesto project between the tubes. In such a case where the core is thefinless type, in which the fines are eliminated between the tubes, orthe type, in which the fins are joined to only one of the adjacenttubes, a draining performance of the condensed water, which is condensedon the outer surface of the core, can be promoted. Therefore, theaccurate temperature measurement of the core is possible, and the goodresponse can be obtained.

Furthermore, in the above embodiments, the refrigerant is the R134arefrigerant. However, the refrigerant of the present invention is notlimited to this type of refrigerant. Even when the other refrigerant,such as the carbon dioxide refrigerant or the R152 refrigerant, is used,the advantages similar to the above described ones can be achieved.However, when the R134a refrigerant is used, the above advantages aremore prominent.

In the above embodiments, the evaporator is used in the refrigerationcycle of the vehicle air conditioning system. However, the presentapplication is also equally application to a heat exchanger in arefrigeration cycle of any other system, which is other than the vehicleair conditioning system.

In the above embodiments, the upstream side and downstream side headertanks are constructed such that the refrigerant is supplied into or isoutputted from the tubes at the interior of the header tank. However,the location, at which the refrigerant is supplied into or is outputtedfrom the tubes, is not limited to the interior of the tank. For example,the location, at which the refrigerant is supplied into or is outputtedfrom the tubes, may be placed on the upstream side or downstream side ofthe interior of the tank rather than placing it completely in theinterior of the tank.

Furthermore, in the above embodiments, the thickness Ta of thedownstream side flow passage row 21, which is measured in the directionof the air flow, is set to be generally the same as the thickness Th ofthe upstream side flow passage row 22, which is measured in thedirection of the air flow. Alternatively, the thickness Ta of thedownstream side flow passage row 21, which is measured in the directionof the air flow, may be made larger than the thickness Th of theupstream side flow passage row 22, which is measured in the direction ofthe air flow. In this way, the cross sectional area of the downstreamside flow passage, at which the dryness of the refrigerant is relativelylarge, is increased. Therefore, the pressure loss of the refrigerant canbe reduced in the entire heat exchanger.

Furthermore, the evaporator of the above respective embodiments includesthe communicating means that communicates between the interior of thefurthermost downstream side header tank 11, which is furthermost fromthe flow inlet 51, and the interior of the furthermost upstream sideheader tank 12, which is furthermost from the flow outlet 52, and thiscommunicating means is placed at the location, which projects laterallyor vertically from the body of the core. In addition to thiscommunication means, it is possible to provide a communication passage,which communicates between the interior of the downstream side headertank 11 and the interior of the upstream side header tank 12.

Additional advantages and modifications will readily occur to thoseskilled in the art. The invention in its broader terms is therefore notlimited to the specific details, representative apparatus, andillustrative examples shown and described.

1. A heat exchanger comprising: a core that includes: a plurality of downstream side flow passage rows, wherein each of the plurality of downstream side flow passage rows is formed with a plurality of downstream side tubes, which extend in a top-to-bottom direction of the core and are placed one after another in a lateral direction of the core to form a plurality of flow passages, respectively, that conduct a flow of refrigerant therethrough and are arranged in a row to form the downstream side flow passage row, and the downstream side flow passage rows are placed side-by-side in the lateral direction of the core on a downstream side in a direction of an air flow, which exchanges heat with the refrigerant; and a plurality of upstream side flow passage rows, wherein each of the plurality of upstream side flow passage rows is formed with a plurality of upstream side tubes, which extend in the top-to-bottom direction of the core and are placed one after another in the lateral direction of the core to form a plurality of flow passages, respectively, that conduct a flow of the refrigerant therethrough and are arranged in a row to form the upstream side flow passage row, and the upstream side flow passage rows are placed side-by-side in the lateral direction of the core on an upstream side of the downstream side flow passage rows in the direction of the air flow; a plurality of downstream side header tanks, each of which supplies the refrigerant to or receives the refrigerant from the downstream side tubes of each corresponding one of the downstream side flow passage rows, wherein the plurality of downstream side header tanks includes: at least one downstream side upper tank, each of which is connected to upper ends of the flow passages of each corresponding one of the downstream side flow passage rows; and at least one downstream side lower tank, each of which is connected to lower ends of the flow passages of each corresponding one of the downstream side flow passage rows; a plurality of upstream side header tanks, each of which supplies the refrigerant to or receives the refrigerant from the upstream side tubes of each corresponding one of the upstream side flow passage rows, wherein the plurality of upstream side header tanks includes: at least one upstream side upper tank, each of which is connected to upper ends of the flow passages of each corresponding one of the upstream side flow passage rows; and at least one upstream side lower tank, each of which is connected to lower ends of the flow passages of each corresponding one of the upstream side flow passage rows; a refrigerant inlet that is located at one lateral side of the core and is communicated with an interior of a corresponding one of the downstream side header tanks to supply the refrigerant to the flow passages of a corresponding one of the downstream side flow passage rows; a refrigerant outlet that is located at the one lateral side of the core and is communicated with an interior of a corresponding one of the upstream side header tanks to output the refrigerant from the flow passages of a corresponding one of the upstream side flow passage rows; at least one downstream side partition wall, each of which is provided in a corresponding one of the downstream side header tanks to partition an interior of the corresponding one of the downstream side header tanks, so that one of the downstream side flow passage rows forms an upflow passage row, in which the flow of the refrigerant becomes an upflow, on one lateral side of the downstream side partition wall, and another one of the downstream side flow passage rows forms a downflow passage row, in which the flow of the refrigerant becomes a downflow, on the other lateral side of the downstream side partition wall; at least one upstream side partition wall, each of which is provided in a corresponding one of the upstream side header tanks to partition an interior of the corresponding one of the upstream side header tanks, so that one of the upstream side flow passage rows forms an upflow passage row, in which the flow of the refrigerant becomes an upflow, on one lateral side of the upstream side partition wall, and another one of the upstream side flow passage rows forms a downflow passage row, in which the flow of the refrigerant becomes a downflow, on the other lateral side of the upstream side partition wall; and a communicating means that is provided at the other lateral side of the core opposite from the refrigerant inlet and the refrigerant outlet and is for communicating between an interior of each corresponding one of the downstream side header tanks, which is connected to a furthermost one of the downstream side flow passage rows that is furthermost from the refrigerant inlet in the lateral direction of the core, and an interior of each corresponding one of the upstream side header tanks, which is connected to a furthermost one of the upstream side flow passage rows that is furthermost from the refrigerant outlet in the lateral direction of the core, wherein: the communicating means is placed at a location that projects from a body of the core in one of the lateral direction and the up-to-bottom direction of the core; a portion of the refrigerant in a furthermost one of the downstream side header tanks, which is furthermost from the refrigerant inlet in the lateral direction of the core, is conducted toward the upstream side of the air flow into a furthermost one of the upstream side header tanks located on an upstream side thereof in the direction of the air flow after flowing through the communicating means and then flows through the furthermost one of the upstream side flow passage rows into an opposed one of the upstream side header tanks, which is opposed to the furthermost one of the upstream side header tanks in the top-to-bottom direction of the core; and a rest of the refrigerant, which remains in the furthermost one of the downstream side header tanks, flows through the furthermost one of the downstream side flow passage rows into an opposed one of the downstream side header tanks, which is opposed to the furthermost one of the downstream side header tanks in the top-to-bottom direction of the core, and then flows toward the upstream side of the air flow into the opposed one of the upstream side header tanks where the rest of the refrigerant is merged with the portion of the refrigerant supplied through the communicating means.
 2. The heat exchanger according to claim 1, wherein: the communicating means includes a lower communication passage that communicates between an interior of a furthermost one of the at least one downstream side lower tank, which is furthermost from the refrigerant inlet in the lateral direction of the core, and an interior of a furthermost one of the at least one upstream side lower tank, which is furthermost from the refrigerant outlet in the lateral direction of the core; the heat exchanger further comprises an upper communication passage that communicates between an interior of a furthermost one of the at least one downstream side upper tank, which is furthermost from the refrigerant inlet in the lateral direction of the core, and an interior of a furthermost one of the at least one upstream side upper tank, which is furthermost from the refrigerant outlet in the lateral direction of the core; and the rest of the refrigerant, which remains in the furthermost one of the at least one downstream side lower tank, flows upwardly through the furthermost one of the downstream side flow passage rows into the furthermost one of the at least one downstream side upper tank and then flows into the furthermost one of the at least one upstream side upper tank through the upper communication passage and is merged with the portion of the refrigerant, which flows from the furthermost one of the at least one downstream side lower tank into the furthermost one of the at least one upstream side lower tank through the lower communication passage and then flows into the furthermost one of the at least one upstream side upper tank thorough the furthermost one of the upstream side flow passage rows.
 3. The heat exchanger according to claim 1, wherein: the communicating means includes an upper communication passage that communicates between an interior of a furthermost one of the at least one downstream side upper tank, which is furthermost from the refrigerant inlet in the lateral direction of the core, and an interior of a furthermost one of the at least one upstream side upper tank, which is furthermost from the refrigerant outlet in the lateral direction of the core; the heat exchanger further comprises a lower communication passage that communicates between an interior of a furthermost one of the at least one downstream side lower tank, which is furthermost from the refrigerant inlet in the lateral direction of the core, and an interior of a furthermost one of the at least one upstream side lower tank, which is furthermost from the refrigerant outlet in the lateral direction of the core; and the rest of the refrigerant, which remains in the furthermost one of the at least one downstream side upper tank, flows downwardly through the furthermost one of the downstream side flow passage rows into the furthermost one of the at least one downstream side lower tank and then flows into the furthermost one of the at least one upstream side lower tank through the lower communication passage and is merged with the portion of the refrigerant, which flows from the furthermost one of the at least one downstream side upper tank into the furthermost one of the at least one upstream side upper tank through the upper communication passage and then flows into the furthermost one of the at least one upstream side lower tank thorough the furthermost one of the upstream side flow passage rows.
 4. The heat exchanger according to claim 1, wherein: the communicating means includes at least one communication passage forming member that has a communication passage therein; and each of the at least one communication passage forming member is formed as a separate component, which is separate from the plurality of downstream side header tanks and the plurality of upstream side header tanks and is assembled integrally to a corresponding one of the plurality of downstream side header tanks and the plurality of upstream side header tanks.
 5. The heat exchanger according to claim 4, wherein at least a portion of each of the at least one communication passage forming member is placed laterally inward of a lateral end of the core in the lateral direction of the core.
 6. The heat exchanger according to claim 5, wherein one of the plurality of downstream side tubes and the plurality of upstream side tubes, which is located at the lateral end of the core, or a side plate, which supports the core, has a longitudinal end portion that is inserted into an interior of a corresponding one of the at least one communication passage forming member.
 7. The heat exchanger according to claim 5, wherein one of the plurality of downstream side tubes and the plurality of upstream side tubes, which is located at the lateral end of the core, or a side plate, which supports the core, has a longitudinal end portion that is inserted into an interior of a corresponding one of the plurality of downstream side header tanks and the plurality of upstream side header tanks.
 8. The heat exchanger according to claim 4, further comprising a lateral end tube, which is placed at a lateral end of the core and does not conduct the refrigerant therethrough, wherein the lateral end tube or a side plate, which supports the core, has a longitudinal end portion that is bent and contacts a corresponding one of the at least one communication passage forming member.
 9. The heat exchanger according to claim 1, wherein at least one communication hole is formed through a wall that partitions between an interior of another furthermost one of the downstream side header tanks and another furthermost one of the upstream side header tanks to communicate therebetween.
 10. The heat exchanger according to claim 1, wherein: the portion of the refrigerant in the furthermost one of the downstream side header tanks is conducted toward the upstream side of the air flow into the furthermost one of the upstream side header tanks through a branching passage having a total passage cross sectional area SI; the rest of the refrigerant in the furthermost one of the downstream side header tanks flows through the furthermost one of the downstream side flow passage rows into the opposed one of the downstream side header tanks, which is opposed to the furthermost one of the downstream side header tanks in the top-to-bottom direction of the core, and then flows toward the upstream side of the air flow into the opposed one of the upstream side header tanks through a merging passage having a total passage cross sectional area S2; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.41≦S1/S2.
 11. The heat exchanger according to claim 10, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as six; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.71≦S1/S2.
 12. The heat exchanger according to claim 10, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as five; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.47≦S1/S2.
 13. The heat exchanger according to claim 10, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as four; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.66≦S1/S2.
 14. The heat exchanger according to claim 10, wherein the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as three.
 15. The heat exchanger according to claim 1, wherein the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, is larger than the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows.
 16. The heat exchanger according to claim 1, wherein each of the plurality of downstream side header tanks and the plurality of upstream side header tanks is formed by integrally joining a plurality of constituent members, which are stacked one after another in the lateral direction of the core.
 17. The heat exchanger according to claim 1, wherein a total thickness of one of the plurality of downstream side header tanks and of an adjacent one of the plurality of upstream side header tanks, which is measured in the direction of the air flow, is equal to or less than 48 mm.
 18. The heat exchanger according to claim 1, wherein a lateral size of the furthermost one of the upstream side flow passage rows, which is measured in the lateral direction of the core, is larger than that of the furthermost one of the downstream side flow passage rows.
 19. The heat exchanger according to claim 1, wherein a lateral size of the furthermost one of the downstream side flow passage rows, which is measured in the lateral direction of the core, is larger than that of the furthermost one of the upstream side flow passage rows.
 20. The heat exchanger according to claim 1, wherein a thickness of the downstream side flow passage rows, which is measured in the direction of the air flow, is larger than that of the upstream side flow passage rows.
 21. A heat exchanger comprising: a core that includes: a plurality of downstream side flow passage rows, wherein each of the plurality of downstream side flow passage rows is formed with a plurality of downstream side tubes, which extend in a top-to-bottom direction of the core and are placed one after another in a lateral direction of the core to form a plurality of flow passages, respectively, that conduct a flow of refrigerant therethrough and are arranged in a row to form the downstream side flow passage row, and the downstream side flow passage rows are placed side-by-side in the lateral direction of the core on a downstream side in a direction of an air flow, which exchanges heat with the refrigerant; and a plurality of upstream side flow passage rows, wherein each of the plurality of upstream side flow passage rows is formed with a plurality of upstream side tubes, which extend in the top-to-bottom direction of the core and are placed one after another in the lateral direction of the core to form a plurality of flow passages, respectively, that conduct a flow of the refrigerant therethrough and are arranged in a row to form the upstream side flow passage row, and the upstream side flow passage rows are placed side-by-side in the lateral direction of the core on an upstream side of the downstream side flow passage rows in the direction of the air flow; a plurality of downstream side header tanks, each of which supplies the refrigerant to or receives the refrigerant from the downstream side tubes of each corresponding one of the downstream side flow passage rows, wherein the plurality of downstream side header tanks includes: at least one downstream side upper tank, each of which is connected to upper ends of the flow passages of each corresponding one of the downstream side flow passage rows; and at least one downstream side lower tank, each of which is connected to lower ends of the flow passages of each corresponding one of the downstream side flow passage rows; a plurality of upstream side header tanks, each of which supplies the refrigerant to or receives the refrigerant from the upstream side tubes of each corresponding one of the upstream side flow passage rows, wherein the plurality of upstream side header tanks includes: at least one upstream side upper tank, each of which is connected to upper ends of the flow passages of each corresponding one of the upstream side flow passage rows; and at least one upstream side lower tank, each of which is connected to lower ends of the flow passages of each corresponding one of the upstream side flow passage rows; a refrigerant inlet that is located at one lateral side of the core and is communicated with an interior of a corresponding one of the downstream side header tanks to supply the refrigerant to the flow passages of a corresponding one of the downstream side flow passage rows; a refrigerant outlet that is located at the one lateral side of the core and is communicated with an interior of a corresponding one of the upstream side header tanks to output the refrigerant from the flow passages of a corresponding one of the upstream side flow passage rows; at least one downstream side partition wall, each of which is provided in a corresponding one of the downstream side header tanks to partition an interior of the corresponding one of the downstream side header tanks, so that one of the downstream side flow passage rows forms an upflow passage row, in which the flow of the refrigerant becomes an upflow, on one lateral side of the downstream side partition wall, and another one of the downstream side flow passage rows forms a downflow passage row, in which the flow of the refrigerant becomes a downflow, on the other lateral side of the downstream side partition wall; at least one upstream side partition wall, each of which is provided in a corresponding one of the upstream side header tanks to partition an interior of the corresponding one of the upstream side header tanks, so that one of the upstream side flow passage rows forms an upflow passage row, in which the flow of the refrigerant becomes an upflow, on one lateral side of the upstream side partition wall, and another one of the upstream side flow passage rows forms a downflow passage row, in which the flow of the refrigerant becomes a downflow, on the other lateral side of the upstream side partition wall; a lower communication passage that is provided at the other lateral side of the core opposite from the refrigerant inlet and the refrigerant outlet and communicates between an interior of a furthermost one of the at least one downstream side lower tank, which is furthermost from the refrigerant inlet in the lateral direction of the core and is connected to a furthermost one of the downstream side flow passage rows that is furthermost from the refrigerant inlet in the lateral direction of the core, and an interior of a furthermost one of the at least one upstream side lower tank, which is furthermost from the refrigerant outlet in the lateral direction of the core and is connected to a furthermost one of the upstream side flow passage rows that is furthermost from the refrigerant outlet in the lateral direction of the core, to conduct a portion of the refrigerant in the furthermost one of the at least one downstream side lower tank into the furthermost one of the upstream side flow passage rows, wherein: the portion of the refrigerant from the furthermost one of the at least one downstream side lower tank flows into the furthermost one of the at least one upstream side lower tank through the lower communication passage and then flows into the furthermost one of the at least one upstream side upper tank after flowing upwardly thorough the furthermost one of the upstream side flow passage rows; a rest of the refrigerant, which remains in the furthermost one of the at least one downstream side lower tank, flows upwardly through the furthermost one of the downstream side flow passage rows into the furthermost one of the at least one downstream side upper tank and then flows into the furthermost one of the at least one upstream side upper tank and is merged with the portion of the refrigerant in the furthermost one of the at least one upstream side upper tank; and a refrigerant inflow opening of the lower communication passage is an inlet of the lower communication passage and opens to an interior of the furthermost one of the at least one downstream side lower tank at a location that is below lower end openings of the downstream side tubes of the furthermost one of the downstream side flow passage rows in the vertical direction.
 22. The heat exchanger according to claim 21, wherein: the portion of the refrigerant in the furthermost one of the downstream side header tanks is conducted toward the upstream side of the air flow into the furthermost one of the upstream side header tanks through a branching passage having a total passage cross sectional area SI; the rest of the refrigerant in the furthermost one of the downstream side header tanks flows through the furthermost one of the downstream side flow passage rows into the opposed one of the downstream side header tanks, which is opposed to the furthermost one of the downstream side header tanks in the top-to-bottom direction of the core, and then flows toward the upstream side of the air flow into the opposed one of the upstream side header tanks through a merging passage having a total passage cross sectional area 52; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.41≦S1/S2.
 23. The heat exchanger according to claim 22, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as six; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.71≦S1/S2.
 24. The heat exchanger according to claim 22, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as five; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.47≦S1/S2.
 25. The heat exchanger according to claim 22, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as four; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.66≦S1/S2.
 26. The heat exchanger according to claim 22, wherein the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as three.
 27. The heat exchanger according to claim 21, wherein the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, is larger than the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows.
 28. The heat exchanger according to claim 21, wherein each of the plurality of downstream side header tanks and the plurality of upstream side header tanks is formed by integrally joining a plurality of constituent members, which are stacked one after another in the lateral direction of the core.
 29. The heat exchanger according to claim 21, wherein a total thickness of one of the plurality of downstream side header tanks and of an adjacent one of the plurality of upstream side header tanks, which is measured in the direction of the air flow, is equal to or less than 48 mm.
 30. The heat exchanger according to claim 21, wherein a lateral size of the furthermost one of the upstream side flow passage rows, which is measured in the lateral direction of the core, is larger than that of the furthermost one of the downstream side flow passage rows.
 31. The heat exchanger according to claim 21, wherein a lateral size of the furthermost one of the downstream side flow passage rows, which is measured in the lateral direction of the core, is larger than that of the furthermost one of the upstream side flow passage rows.
 32. The heat exchanger according to claim 21, wherein a thickness of the downstream side flow passage rows, which is measured in the direction of the air flow, is larger than that of the upstream side flow passage rows.
 33. A heat exchanger comprising: a core that includes: a plurality of downstream side flow passage rows, wherein each of the plurality of downstream side flow passage rows is formed with a plurality of downstream side tubes, which extend in a top-to-bottom direction of the core and are placed one after another in a lateral direction of the core to form a plurality of flow passages, respectively, that conduct a flow of refrigerant therethrough and are arranged in a row to form the downstream side flow passage row, and the downstream side flow passage rows are placed side-by-side in the lateral direction of the core on a downstream side in a direction of an air flow, which exchanges heat with the refrigerant; and a plurality of upstream side flow passage rows, wherein each of the plurality of upstream side flow passage rows is formed with a plurality of upstream side tubes, which extend in the top-to-bottom direction of the core and are placed one after another in the lateral direction of the core to form a plurality of flow passages, respectively, that conduct a flow of the refrigerant therethrough and are arranged in a row to form the upstream side flow passage row, and the upstream side flow passage rows are placed side-by-side in the lateral direction of the core on an upstream side of the downstream side flow passage rows in the direction of the air flow; a plurality of downstream side header tanks, each of which supplies the refrigerant to or receives the refrigerant from the downstream side tubes of each corresponding one of the downstream side flow passage rows, wherein the plurality of downstream side header tanks includes: at least one downstream side upper tank, each of which is connected to upper ends of the flow passages of each corresponding one of the downstream side flow passage rows; and at least one downstream side lower tank, each of which is connected to lower ends of the flow passages of each corresponding one of the downstream side flow passage rows; a plurality of upstream side header tanks, each of which supplies the refrigerant to or receives the refrigerant from the upstream side tubes of each corresponding one of the upstream side flow passage rows, wherein the plurality of upstream side header tanks includes: at least one upstream side upper tank, each of which is connected to upper ends of the flow passages of each corresponding one of the upstream side flow passage rows; and at least one upstream side lower tank, each of which is connected to lower ends of the flow passages of each corresponding one of the upstream side flow passage rows; a refrigerant inlet that is located at one lateral side of the core and is communicated with an interior of a corresponding one of the downstream side header tanks to supply the refrigerant to the flow passages of a corresponding one of the downstream side flow passage rows; a refrigerant outlet that is located at the one lateral side of the core and is communicated with an interior of a corresponding one of the upstream side header tanks to output the refrigerant from the flow passages of a corresponding one of the upstream side flow passage rows; at least one downstream side partition wall, each of which is provided in a corresponding one of the downstream side header tanks to partition an interior of the corresponding one of the downstream side header tanks, so that one of the downstream side flow passage rows forms an upflow passage row, in which the flow of the refrigerant becomes an upflow, on one lateral side of the downstream side partition wall, and another one of the downstream side flow passage rows forms a downflow passage row, in which the flow of the refrigerant becomes a downflow, on the other lateral side of the downstream side partition wall; at least one upstream side partition wall, each of which is provided in a corresponding one of the upstream side header tanks to partition an interior of the corresponding one of the upstream side header tanks, so that one of the upstream side flow passage rows forms an upflow passage row, in which the flow of the refrigerant becomes an upflow, on one lateral side of the upstream side partition wall, and another one of the upstream side flow passage rows forms a downflow passage row, in which the flow of the refrigerant becomes a downflow, on the other lateral side of the upstream side partition wall; and an upper communication passage that is provided at the other lateral side of the core opposite from the refrigerant inlet and the refrigerant outlet and communicates between an interior of a furthermost one of the at least one downstream side upper tank, which is furthermost from the refrigerant inlet in the lateral direction of the core and is connected to a furthermost one of the downstream side flow passage rows that is furthermost from the refrigerant inlet in the lateral direction of the core, and an interior of a furthermost one of the at least one upstream side upper tank, which is furthermost from the refrigerant outlet in the lateral direction of the core and is connected to a furthermost one of the upstream side flow passage rows that is furthermost from the refrigerant outlet in the lateral direction of the core, to conduct a portion of the refrigerant in the furthermost one of the at least one downstream side upper tank into the furthermost one of the upstream side flow passage rows, wherein: the portion of the refrigerant from the furthermost one of the at least one downstream side upper tank flows into the furthermost one of the at least one upstream side upper tank through the upper communication passage and then flows into the furthermost one of the at least one upstream side lower tank after flowing downwardly thorough the furthermost one of the upstream side flow passage rows; a rest of the refrigerant, which remains in the furthermost one of the at least one downstream side upper tank, flows downwardly through the furthermost one of the downstream side flow passage rows into the furthermost one of the at least one downstream side lower tank and then flows into the furthermost one of the at least one upstream side lower tank and is merged with the portion of the refrigerant in the furthermost one of the at least one upstream side lower tank; and a refrigerant inflow opening of the upper communication passage is an inlet of the upper communication passage and opens to an interior of the furthermost one of the at least one downstream side upper tank at a location that is above upper end openings of the downstream side tubes of the furthermost one of the downstream side flow passage rows in the vertical direction.
 34. The heat exchanger according to claim 33, wherein: the portion of the refrigerant in the furthermost one of the downstream side header tanks is conducted toward the upstream side of the air flow into the furthermost one of the upstream side header tanks through a branching passage having a total passage cross sectional area S1; the rest of the refrigerant in the furthermost one of the downstream side header tanks flows through the furthermost one of the downstream side flow passage rows into the opposed one of the downstream side header tanks, which is opposed to the furthermost one of the downstream side header tanks in the top-to-bottom direction of the core, and then flows toward the upstream side of the air flow into the opposed one of the upstream side header tanks through a merging passage having a total passage cross sectional area S2; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.41≦S1/S2.
 35. The heat exchanger according to claim 34, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as six; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.71≦S1/S2.
 36. The heat exchanger according to claim 34, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as five; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.47≦S1/S2.
 37. The heat exchanger according to claim 34, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as four; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.66≦S1/S2.
 38. The heat exchanger according to claim 34, wherein the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as three.
 39. The heat exchanger according to claim 33, wherein the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, is larger than the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows.
 40. The heat exchanger according to claim 33, wherein each of the plurality of downstream side header tanks and the plurality of upstream side header tanks is formed by integrally joining a plurality of constituent members, which are stacked one after another in the lateral direction of the core.
 41. The heat exchanger according to claim 33, wherein a total thickness of one of the plurality of downstream side header tanks and of an adjacent one of the plurality of upstream side header tanks, which is measured in the direction of the air flow, is equal to or less than 48 mm.
 42. The heat exchanger according to claim 33, wherein a lateral size of the furthermost one of the upstream side flow passage rows, which is measured in the lateral direction of the core, is larger than that of the furthermost one of the downstream side flow passage rows.
 43. The heat exchanger according to claim 33, wherein a lateral size of the furthermost one of the downstream side flow passage rows, which is measured in the lateral direction of the core, is larger than that of the furthermost one of the upstream side flow passage rows.
 44. The heat exchanger according to claim 33, wherein a thickness of the downstream side flow passage rows, which is measured in the direction of the air flow, is larger than that of the upstream side flow passage rows.
 45. A heat exchanger comprising: a core that includes: a plurality of downstream side flow passage rows, wherein each of the plurality of downstream side flow passage rows is formed with a plurality of downstream side tubes, which extend in a top-to-bottom direction of the core and are placed one after another in a lateral direction of the core to form a plurality of flow passages, respectively, that conduct a flow of refrigerant therethrough and are arranged in a row to form the downstream side flow passage row, and the downstream side flow passage rows are placed side-by-side in the lateral direction of the core on a downstream side in a direction of an air flow, which exchanges heat with the refrigerant; and a plurality of upstream side flow passage rows, wherein each of the plurality of upstream side flow passage rows is formed with a plurality of upstream side tubes, which extend in the top-to-bottom direction of the core and are placed one after another in the lateral direction of the core to form a plurality of flow passages, respectively, that conduct a flow of the refrigerant therethrough and are arranged in a row to form the upstream side flow passage row, and the upstream side flow passage rows are placed side-by-side in the lateral direction of the core on an upstream side of the downstream side flow passage rows in the direction of the air flow; a plurality of downstream side header tanks, each of which supplies the refrigerant to or receives the refrigerant from the downstream side tubes of each corresponding one of the downstream side flow passage rows, wherein the plurality of downstream side header tanks includes: at least one downstream side upper tank, each of which is connected to upper ends of the flow passages of each corresponding one of the downstream side flow passage rows; and at least one downstream side lower tank, each of which is connected to lower ends of the flow passages of each corresponding one of the downstream side flow passage rows; a plurality of upstream side header tanks, each of which supplies the refrigerant to or receives the refrigerant from the upstream side tubes of each corresponding one of the upstream side flow passage rows, wherein the plurality of upstream side header tanks includes: at least one upstream side upper tank, each of which is connected to upper ends of the flow passages of each corresponding one of the upstream side flow passage rows; and at least one upstream side lower tank, each of which is connected to lower ends of the flow passages of each corresponding one of the upstream side flow passage rows; a refrigerant inlet that is located at one lateral side of the core and is communicated with an interior of a corresponding one of the downstream side header tanks to supply the refrigerant to the flow passages of a corresponding one of the downstream side flow passage rows; a refrigerant outlet that is located at the one lateral side of the core and is communicated with an interior of a corresponding one of the upstream side header tanks to output the refrigerant from the flow passages of a corresponding one of the upstream side flow passage rows; at least one downstream side partition wall, each of which is provided in a corresponding one of the downstream side header tanks to partition an interior of the corresponding one of the downstream side header tanks, so that one of the downstream side flow passage rows forms an upflow passage row, in which the flow of the refrigerant becomes an upflow, on one lateral side of the downstream side partition wall, and another one of the downstream side flow passage rows forms a downflow passage row, in which the flow of the refrigerant becomes a downflow, on the other lateral side of the downstream side partition wall; at least one upstream side partition wall, each of which is provided in a corresponding one of the upstream side header tanks to partition an interior of the corresponding one of the upstream side header tanks, so that one of the upstream side flow passage rows forms an upflow passage row, in which the flow of the refrigerant becomes an upflow, on one lateral side of the upstream side partition wall, and another one of the upstream side flow passage rows forms a downflow passage row, in which the flow of the refrigerant becomes a downflow, on the other lateral side of the upstream side partition wall; and a communicating means that is provided at the other lateral side of the core opposite from the refrigerant inlet and the refrigerant outlet and is for communicating between an interior of each corresponding one of the downstream side header tanks, which is connected to a furthermost one of the downstream side flow passage rows that is furthermost from the refrigerant inlet in the lateral direction of the core, and an interior of each corresponding one of the upstream side header tanks, which is connected to a furthermost one of the upstream side flow passage rows that is furthermost from the refrigerant outlet in the lateral direction of the core, wherein: the core has an upstream side lateral plane and a downstream side lateral plane, which are located on the upstream side and the downstream side, respectively, in the direction of the air flow; the core is tilted toward the upstream side in the direction of the air flow such that the upstream side lateral plane is closer to an imaginary horizontal plane, which is placed vertically below the at least one upstream side lower tank, in comparison to the downstream side lateral plane; a portion of the refrigerant in a furthermost one of the downstream side header tanks, which is furthermost from the refrigerant inlet in the lateral direction of the core, is conducted toward the upstream side of the air flow into a furthermost one of the upstream side header tanks located on an upstream side thereof in the direction of the air flow after flowing through the communicating means and then flows through the furthermost one of the upstream side flow passage rows into an opposed one of the upstream side header tanks, which is opposed to the furthermost one of the upstream side header tanks in the top-to-bottom direction of the core; and a rest of the refrigerant, which remains in the furthermost one of the downstream side header tanks, flows through the furthermost one of the downstream side flow passage rows into an opposed one of the downstream side header tanks, which is opposed to the furthermost one of the downstream side header tanks in the top-to-bottom direction of the core, and then flows toward the upstream side of the air flow into the opposed one of the upstream side header tanks where the rest of the refrigerant is merged with the portion of the refrigerant supplied through the communicating means.
 46. The heat exchanger according to claim 45, wherein: the portion of the refrigerant in the furthermost one of the downstream side header tanks is conducted toward the upstream side of the air flow into the furthermost one of the upstream side header tanks through a branching passage having a total passage cross sectional area S1; the rest of the refrigerant in the furthermost one of the downstream side header tanks flows through the furthermost one of the downstream side flow passage rows into the opposed one of the downstream side header tanks, which is opposed to the furthermost one of the downstream side header tanks in the top-to-bottom direction of the core, and then flows toward the upstream side of the air flow into the opposed one of the upstream side header tanks through a merging passage having a total passage cross sectional area S2; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.41≦S1/S2.
 47. The heat exchanger according to claim 46, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as six; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.71≦S1/S2.
 48. The heat exchanger according to claim 46, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as five; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.47≦S1/S2.
 49. The heat exchanger according to claim 46, wherein: the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as four; and the branching passage and the merging passage are constructed to satisfy a relationship of 0.66≦S1/S2.
 50. The heat exchanger according to claim 46, wherein the flow of the refrigerant in the furthermost one of the downstream side flow passage rows and the flow of the refrigerant in the furthermost one of the upstream side flow passage rows are directed in a common direction and are thereby counted as one refrigerant flow path, and the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, and the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows, are counted as the number of refrigerant flow paths in the remaining downstream side flow passage rows and the remaining upstream side flow passage rows, so that the total number of the refrigerant flow paths in the core is counted as three.
 51. The heat exchanger according to claim 45, wherein the number of the remaining downstream side flow passage rows, which are other than the furthermost one of the downstream side flow passage rows, is larger than the number of the remaining upstream side flow passage rows, which are other than the furthermost one of the upstream side flow passage rows.
 52. The heat exchanger according to claim 45, wherein each of the plurality of downstream side header tanks and the plurality of upstream side header tanks is formed by integrally joining a plurality of constituent members, which are stacked one after another in the lateral direction of the core.
 53. The heat exchanger according to claim 45, wherein a total thickness of one of the plurality of downstream side header tanks and of an adjacent one of the plurality of upstream side header tanks, which is measured in the direction of the air flow, is equal to or less than 48 mm.
 54. The heat exchanger according to claim 45, wherein a lateral size of the furthermost one of the upstream side flow passage rows, which is measured in the lateral direction of the core, is larger than that of the furthermost one of the downstream side flow passage rows.
 55. The heat exchanger according to claim 45, wherein a lateral size of the furthermost one of the downstream side flow passage rows, which is measured in the lateral direction of the core, is larger than that of the furthermost one of the upstream side flow passage rows.
 56. The heat exchanger according to claim 45, wherein a thickness of the downstream side flow passage rows, which is measured in the direction of the air flow, is larger than that of the upstream side flow passage rows. 